SimpleCache is a very simple cache. For more advanced caching solutions (based on a slightly different concept) take a look at ZCache and GenericCache.
SimpleCache is different from ZCache in that it has a concept of dependencies. A SimpleCache can depend on a list of Zope objects, and whenever one of those objects changed and the cache is requested, the cached data is refreshed. Unlike ZCache, SimpleCache has no timeout behavior either, and does not attempt to make the browser cache any output. It's truly very simple.