In more detail
A context window is an AI’s working memory — everything it can ‘see’ at once: your question, the conversation so far, and any documents you pasted in. Think of it as a desk that only fits so many papers. Anything that doesn’t fit on the desk simply doesn’t exist to the model.
It matters because it sets very real limits. A small window means the AI forgets the start of a long chat or can’t take in your whole report. Bigger windows let it hold entire books in mind at once — though everything on the desk is measured, and paid for, in tokens.
Goes with