MediaWiki talk:Refresh

The text of this message page is what will be displayed on the Refresh tab. Clicking refresh will allow you to purge the current cache of that page, forcing an update of the cache contents. This isn't generally needed, the cache will usually update anytime the page has been changed, there are exceptions however, such as if an image is updated with a new image (same name).

http://www.mediawiki.org/wiki/Manual:File_cache#Refresh_tab