There are several methods by which caching can be used
This turns on caching for the entire website, but only for those pages and snippets which have been permitted to cache
Selecting the 'Cache this page' checkbox when editing a page ensures it gets cached. Editing a page will refresh the cache for that page.
Selecting the 'Cache this page' checkbox when editing a snippet ensures it gets cached. Editing a snippet will refresh the cache for that snippet.