Here's a common frustration: you spend an hour having a detailed conversation with an AI about your project architecture, close the browser, and come back the next day. It remembers nothing. Even within a single conversation, paste in a 50-page document and ask about something on page 3, and the model might miss it entirely. AI models don't have memory the way humans do. They have a context window, a fixed-size buffer of tokens they can "see" at once. Everything outside that window simply doesn't exist to the model. Understanding this limitation, and the clever strategies engineers use to work around it, is essential for building effective AI applications.