Thirty terms, one mechanic underneath all of them, in three levels. Level one is the model and the limits that ship with it. Level two is the software wrapped around the model. That layer is what you are actually being sold. Level three is the vocabulary of agents, and it is the level that decides whether the thing you buy belongs anywhere near your dispatch board.
Level one: the machine you are renting
1. Large language model
What gets sold to you as AI is almost always a large language model, and a large language model is an extremely sophisticated autocomplete. It predicts the most likely next word to answer whatever you asked. That single mechanic explains everything else on this page, including the parts that go wrong.
2. Prompt
Whatever you send it. A question, an instruction, a request. The model has nothing else to go on, so the answer tracks the prompt. Paste in a tenant’s email and ask for a draft reply, and you have written one.
3. Token
Pieces of words, and the unit everything is measured in. Car is one token. Unbelievable is three. What you send is input tokens, what comes back is output tokens, and a heavier request burns more of both.
4. Model
Each company builds its own version and calls it a model. ChatGPT is OpenAI’s, Claude is Anthropic’s, Gemini is Google’s, all the same thing built by different teams racing each other, which is why it feels like something new lands every other day. Each one ships in sizes. Anthropic has four: Haiku is small, fast and cheap, Sonnet sits in the middle, Opus is more capable and slower, and Fable sits above Opus as the most expensive by a wide margin. Bigger is more capable, slower and dearer. Smaller is faster, cheaper and a lot worse at anything complicated. For any job you hand over, the size it needs matters more than the badge on it.
5. Open and closed models
Closed means you never hold the model. Requests go to the company that made it and answers come back. Open means anyone can download it, run it on their own machine and modify it for free. Meta’s Llama is open. Open buys control and privacy. Closed is more powerful and more polished, and as of 2026 it is what the average person actually uses.
6. Parameters and training
Inside a model are billions of tiny dials. Each dial is a parameter, and one dial on its own means nothing, but together they hold how words relate and how ideas connect. Training is the trial and error that settles every dial into the position that predicts language well. More dials hold more patterns, and that is all “a bigger model” means.
7. Multimodal
Beyond text. Send a photo of a cracked flat roof or a compressor nameplate and the model describes what it sees, usually pretty accurately. That is what puts a field tech’s camera into the workflow instead of an inbox. Multimodal is the word for it.
8. Context window
Think of a desk, measured in tokens. Your prompt, the chat so far, the files you dropped in, every reply it already gave, all of it has to fit on there. Fill the desk and two things happen. The oldest material falls off the edge, which is why a long chat forgets what you told it at the start, and the answers get worse the fuller it gets. Start a new chat and you get a clean context window.
9. Context compression
Most models now summarise the conversation up to a point and carry the summary forward instead of the whole thing, which clears desk space so you can keep going. A summary is smaller than the thing it summarises, so you continue with less detail than you had.
10. Knowledge cutoff
It learned from a giant pile of text up to a date, then froze. Ask about last week and it has no idea, which is why newer models search the web to bridge the gap. Anything that happened in your business after that date has to be handed to it.
11. Hallucination
Confident, convincing and completely wrong. Ask ChatGPT how many R’s are in strawberry and it answers two. Lying would require knowing better, and it does not know better, because it predicts plausible words with none of the logic you would use to check them. Strawberry is harmless. A made-up clause in a lease summary that reads perfectly is the same hallucination with your money behind it.
Level two: the software wrapped around it
12. System prompt
A second prompt you never see, running behind whatever app you are in. It tells the model whether it is a coding assistant or a customer service bot, what it is allowed to help with, and what to refuse. On its own the model has no idea who it is supposed to be. Write instructions into a custom GPT and you have written a small system prompt.
13. Memory
During a conversation the app quietly writes down anything that mattered and keeps it after the chat ends. Next time, before it replies, it flips through the notebook and pulls the important bits back onto the desk. That is how it knows where you work or that you are vegetarian, and in some apps you see a memory updated note when it saves something. The notebook is memory.
14. Reasoning
Early models blurted out the first answer that came to mind. Newer ones write their thinking down step by step first, so each step becomes part of what they can see and the next step has something to stand on. By the time it answers it is standing on a chain of work it already did. The trade is time and tokens, and on anything genuinely hard reasoning earns it.
15. API
How one piece of software talks to another. One program sends a request, the other does the work and sends back a response. Your CRM has an API, your field service software has one, and that is the plumbing a model reaches them through.
16. Wrapper
An app sitting on top of someone else’s model, reaching it through that API. The ChatGPT app is a wrapper. Perplexity is a wrapper. Cursor is the argument everyone has, and technically it still is one. Own name, own logo, own interface, engine built by someone else. A huge number of AI startups are wrappers, and the value they add on top gets thinner every time the models improve.
17. Tool
Left alone, a model answers questions and writes things. It cannot look something up online or send an email. A tool is anything you allow it to use to get a real task done, reached through an API. Send the email. Book the slot. Pull the invoice.
18. AI agent
Reasoning plus tools. A chatbot answers you. An agent takes a goal and works the steps on its own until the job is done. Almost everyone who thinks they have used AI has used the chatbot.
Level three: what changes once it can act
19. Agentic loop
How an agent actually runs. Look at the goal, pick the next step, take it with a tool, check what happened, go again until done. The search comes back empty so it tries a different one. Something fails so it adjusts and goes at it again. Same shape as reasoning, except each pass changes something outside the chat.
20. RAG
Out of the box the model knows nothing about your business, your documents or your data. RAG, retrieval augmented generation, fixes that by letting it look things up in your files first and answer from what it found. An open book exam instead of a closed one. It is how an agent knows your warranty terms and your escalation policy, and when the policy changes you edit the document rather than retrain anything.
21. Vector database
Where those documents sit so they can be searched by meaning instead of by keyword. A library organised so automobile lands next to car and nowhere near banana. A tenant writes “no heat” and you want the furnace pages back, not every document containing the word no. Vector databases are what make that work.
22. Embeddings
The numbers underneath the meaning. Text goes in, a string of numbers comes out, and similar meanings end up with similar numbers. Your question gets turned into numbers too, and the database hands back the closest ones.
23. Skill
Step-by-step know-how for one kind of task, packaged once. Without it the agent works out how to do the job from scratch every time. With it, it follows proven steps and holds the same quality. If you want every service report filled out the same way, package the steps once as a skill and stop re-explaining them in the prompt.
24. MCP
Every app has its own API, its own configuration and its own way in, and wiring an agent to each of them separately becomes a hassle at scale. MCP is the USB-C of the agentic world. One standard doorway in front of every app’s API, so the agent learns one way in rather than a new one per tool. The API is still there underneath.
25. Guardrails
With a chatbot the worst case is that it says something dumb. With an agent the worst case is an email to the wrong client, money moved to the wrong place, files deleted. Guardrails are the limits and rules you put around it. They block off-limit requests, check for private data leaving, and cap token spend before a looping agent burns hundreds of dollars.
26. Prompt injection
The biggest external security hole, and it comes straight from how agents work. An agent has to read the outside world, and it cannot reliably tell instructions from you apart from words it is only supposed to be reading. An attacker hides a command inside a document or a web page the agent has been sent to read, and the agent treats that hidden command as an order from you.
27. AI workflow
An agent picks its own steps, which is powerful and unpredictable. Ask it the same task three times and it might take three different paths. You run a company on SOPs, and for repetitive work you want the SOP followed every time. That is an AI workflow. Nobody wants a creative approach to the accounting.
28. Multi-agent system
Ask one agent for a full competitor analysis and it does the research, the pricing, the charts and the writing inside a single context window, and quality drops as the desk fills. Split the job instead. One agent researches, one does pricing, one does the visuals, each with its own context window and its own instance. The output is better and the bill is bigger.
29. Orchestrator
Someone has to run the other agents, and that someone is another agent. The orchestrator breaks the goal down, schedules and delegates, hands out context, then checks and merges the work as it comes back. OpenClaw and Hermes agents are orchestrators.
30. Autonomy
Everything above still waits for a human to start it. An autonomous agent starts itself, either on a schedule or on a trigger. OpenClaw calls its version a heartbeat. The agent wakes itself up, checks your files, inbox and database for anything that changed, does what you told it to do about it, and loops back round.
What to ask before you buy one
When someone pitches you an agent for after-hours dispatch or lease renewals, start with the guardrails. What is it not allowed to do, and what happens when it tries? Then ask what it can reach, meaning which of your documents it retrieves and which tools it is wired to. A vague answer to the first question means you are buying a chatbot that can send email.