Context Window
The amount of text an AI can remember and consider at one time during a single conversation.
In Plain English
The context window is like the AI's short-term memory. Just as a human might forget the beginning of a very long, rambling story, an AI will forget earlier parts of a conversation if the context window is exceeded. If you paste a 100-page document into an AI with a small context window, it will only remember the last few pages. Newer models have massive context windows, allowing them to read entire books at once.
Real-World Example
Pasting a 10-page PDF into an AI and asking it to summarize the main points, which it can do because the text fits in its context window.