Caching background in the context of Plone

Zope 2 is an application server. Therefore, every page it delivers involves "doing work", which results in server and network load. If possible, to conserve the system resources, you may want to cache your site's content as much as is practical and possible.

Caching agents store resources needed to serve the site's content and answer site requests with these resources, until the browser or caching agent is no longer able to do so (for example, when a caching rule tells the browser or caching agent that the page has expired).

At this point, it must contact the application server again for new data.