An AI model is a system trained on a huge amount of text that predicts what comes next. The app is what you type into. The model is what answers.
ChatGPT is an app built on top of the GPT-5 model. The Claude desktop app sits on Anthropic’s model. The model is the intelligence layer, where the thinking happens and where information gets retrieved.
Is ChatGPT the same thing as GPT-5?
No. ChatGPT is the app, GPT-5 is the model underneath it. Three or four years ago ChatGPT was a category of one, so nobody had to keep the two names apart. Now you have Claude, Gemini and Chinese models like DeepSeek, and people use the word “model” for the apps too.
Some apps are built by the lab that built the model. ChatGPT by OpenAI, the Claude app by Anthropic. Others take a model from OpenAI or Anthropic and build a narrower product on top of it. Perplexity and Cursor work that way. Those are wrappers, and they get their own lesson next.
Which companies actually build the models?
Five labs.
| Lab | Models | What to know |
|---|---|---|
| OpenAI | GPT-5, GPT-5 mini, o-series | The leader in the space. GPT-5 is the largest and smartest, mini is the cheap small tier, and the o-series are the reasoning models. None of them are open weight, so you cannot download one and run it yourself. |
| Anthropic | Haiku, Sonnet, Opus | Smallest to largest, one family. Most people run Sonnet as the daily driver. |
| Gemini Flash, Gemini Pro | Flash is the one you point at a queue of after-hours messages that all have to be sorted before 9am. Gemini Pro takes the harder thinking and takes longer over it. | |
| Meta | Llama series | Open source by default. Any engineer or any company can download it and run it on their own hardware. |
| xAI | Grok | An up and comer. Not used as much as the other four. |
DeepSeek is the Chinese model that comes up most in these conversations. It is not one of the five above.
Is a model the same as an LLM?
An LLM, a large language model, is one kind of model. It is the kind that reads and writes text, and it is the kind every name in that table refers to. There are also models that only handle images, and models that only handle speech. The big labs now ship single models that take text, images and audio together, which is what multi-modal means.
Why every lab sells a small model
Larger, smarter models are slower and more expensive. That is the whole reason the tiers exist.
Sorting an after-hours message into emergency or not emergency is a yes or no question over a short block of text. Cleaning up a transcript is the same class of job: the answer is nearly determined by the input, and there is nothing to work out. Neither one needs your most expensive model. Complex thinking across several sources arriving at once is what the big model is for.
What you save on a small model is a per-token rate. The same ten-page document is the same number of tokens whether Haiku, Sonnet or Opus reads it. What changes is the price you are charged for each of those tokens, which is why running every job on the top tier costs far more than the work is worth.
The framework for choosing is a triangle with intelligence, speed and cost at the corners. You get two.
- Smart and cheap, and it will be slow.
- Cheap and fast, and it will not be that smart.
- Smart and fast, and you will pay for it.
So ask how much intelligence the job needs, how fast it has to finish, and what you are willing to pay. Asked in that order, most jobs answer themselves. After-hours triage runs all night, has to reply before the caller gives up, and comes down to one yes or no call, so it lives on the cheap fast tier and stays there.
How do you know which model is best right now?
Look at a leaderboard. We use LMArena, a table of models ranked by category, writing for example, based on testers voting on which output they preferred.
Do that once, not weekly. Two years ago you had to keep up, because the gap between the models was large enough to change what you could build. Today they are all pretty good, and the labs compete on the tools they build around a model more than on the intelligence inside it.
So pick a tier per job. The cheap fast model for the high-volume triage work, the big one for the handful of calls where being wrong costs you a truck roll.