The working copy provides an easy way to make changes to content, online or offline, and review and update the changes before replacing the original content.
Checking out a content item locks the original item. Roll your mouse
over the lock icon associated with a content item to see who checked it
out. The icon 
indicates it is checked out by you
and 
indicates it is checked out by another user.
Users can view both the original version and the working copy of a content item. The working copy remains the same as the original unless you upload your changes. You can update the working copy to allow others to see your changes without updating the original content.
Once you complete your edits, you must check in the working copy to update the original content item.