The recycle bin in Catalyst serves as storage for items that have been deleted. Items can stay in the Recycle Bin indefinitely, however, only the most recent 300 items are available. You can access the Recycle Bin by going to Administration => Recycle Bin.
The recycle bin will allow users to restore items that have been deleted by clicking the restore button next to the item. Nested items will give a warning that parent items should be restored if they were deleted also, and will allow you to restore that item from the warning window.