HTTP requests to your web application usually entail database access, data processing, and template rendering. This is much more expensive in terms of processing than serving a static website.

The overhead in some requests can be significant when your site starts getting more and more traffic. This is where caching becomes precious. By caching queries, calculation results, or rendered content in an HTTP request, you will avoid cost-expensive operations in the following requests. This translates into shorter response times and less processing on the server side.

Django includes a robust cache system that allows you to cache data with different levels of granularity. You can cache a single query, the output of a specific view, parts of rendered template content, or your entire site. Items are stored in the cache system for a default time. You can specify the default timeout for cached data.

This is how you will usually use the cache framework when your application gets an HTTP request:

1. Try to find the requested data in the cache
2. If found, return the cached data
3. If not found, perform the following steps:
   1. Perform the query or processing required to obtain the data
   2. Save the generated data in the cache
   3. Return the data

You can read detailed information about Django's cache system at https://docs.djangoproject.com/en/2.0/topics/cache/.