Three things you need to check periodically (for example monthly) to maintain your Joomla website health.
This tool allows Joomla administrators to unlock items currently locked whether they are in-use by other users or the item wasn't closed properly. Make sure no one is busy editing any items before you perform a global check-in. When a Global Check-in is done,all items are checked in, including those currently being edited.
This is useful, for example, if an article is locked by a user who opened it for editing and never finished the editing session. In this case, other users are not able to edit this article. Performing a Global Check-in releases all such items.
This tool helps to clear cache files from the cache folders if enabled under the site Global Configuration settings. This tool will delete all Cache files from the cache folders, including current ones, from your web server. As admin functions are cached too, some cache folders might appear as if they were not cleaned because they get recreated before cache content is rescanned after this action.
Cache files are temporary files that are created to improve the performance of your site. If you have made significant changes to your web site, such as changing your Template or Language, your cache files may be outdated. To avoid any problems caused by outdated cache files, you can delete all the cache files.
Because this process deletes all Cache files, the website may be a little slower immediately after running Clear Cache. Once this process is complete, users lose the benefit of using the cache files until they are re-created by Joomla to be up to date with your current site.
This tool is used for deleting the expired cache files if caching is enabled. This tool will purge all expired cache files from the cache folders. Cache files are temporary files that are created to improve the performance of your site. Cache files that are still current are not purged.
Because this process has to check each cache file individually, it is slower and requires more system resources. Once the purge process is complete there should be no loss in speed for your users, because all up to date cache files are still available for your current Joomla website.
In contrast, the Clean Cache option runs more quickly since it deletes all of the files stored in each cache folder. However, the website may be a little slower immediately after running Clean Cache, since all cache files including current ones are removed, so users lose the benefit of using the cache files until they are re-created by Joomla to be up to date with your current site.