The tools most people meet first are chat assistants: a text box where you type a question or request and get a written reply. Behind that box is an LLM. The three you will hear about most are:
There are others, but these three are the general-purpose assistants a lot of people use daily.
It is easy to think of these as completely separate products, but under the hood they are the same idea: a large language model with a chat interface wrapped around it. You type, it generates a reply, you type again. Each has its own personality and strengths, and which one is "best" shifts every few months as new versions come out.
For a beginner, the practical takeaway is reassuring. Learn to work with one and you can work with all of them, because the way you ask - the actual skill this course teaches - is the same across every chat assistant.
Do not get too attached to any single product name or version number. This field moves fast. New models arrive constantly, leaders trade places, and today's best choice may not be next year's. The durable skill is understanding what these tools are and how to use them well, which is exactly what the rest of the course builds. Next: the tools that are not just a chat box.