When a user in the backend of Joomla access an article or module in the site, the access to that particular part of Joomla is blocked to any other users.
Sometimes it is necessary to clear this blocked access as a users' session may have expired or the article or module that was being edited didn't have the access to the item closed correctly.
Navigating to Global check-in from the menu will clear all access restrictions due to another user accessing the content item and allow others to gain access.
When site cache is turned on, there are times when you will want to clear the cache in order to see changes to content and the website.
Navigate to the menu item and select clear cache. This wil clear it and generate a new cache of the pages that you are viewing and testing on the website
Purge Expired Cache
Cache within Joomla has an expiry time. This time is setup in the configuration of the site and the caching pluggins. When these cache files expire, Joomla will create new cache files. From time to time you will need to purge the cache as it will be taking up disk space.
NAvigate to the purge expired cache menu item and all expired cache items will be removed.