A context window is the amount of input a model can consume in a single request.
A larger context window lets you send more information into one request, but it does not mean the model remembers anything after the request ends.
That is why products with long context windows can still feel forgetful across sessions.
Context windows are the container. Retrieval and memory decide what deserves to go inside that container. Good context engineering matters more than simply making the container larger.
In practice, teams need all three concepts: a model window, a retrieval path, and a memory layer.
Use these glossary pages and commercial landing pages to move from definition to implementation.