Context window
The context window is the amount of text a language model can read and remember at one time.
What it tells you about a developer
A developer who talks about managing the context window has built something big enough to hit the limit. That points to real production experience with a model rather than demo work.
A model's context window is named for the same reason a window limits what a person can see outside: everything inside it is visible to the model, and everything outside it is not. A larger context window lets a model read a longer document, a longer conversation, or more surrounding code before answering. When a model gives an inconsistent answer partway through a long conversation, the cause is often that earlier parts of the conversation have fallen outside the context window.