Joomla:

Global Check-in

When an item is checked out and it is not saved or cancelled correctly (such as with a connection error or the use of "back" buton in the browser), it will remain checked out, and thus uneditable for all users (including the user who already checked the item out). Performing a Global Check-in will make those items available again. This option is only available in the Administrator (Back-end) (and only to Super Administrators). Logged in users can check-in items that they personally have checked out from the 'user menu'.

Group

Collection of user levels, classified as either Site (Front-end) or Administrator (Back-end). See also: Administrator (Back-end), Site (Front-end).

Not Directly Joomla Related:

Group

One of three sets of permissions on a Unix web server. Different 'rights' to carry out actions are available depending upon whether you are the 'owner' of a file, in the same 'group' as the owner, or for everyone else.