The Clipboard is made up of two parts of the interface. Firstly, there is the section on the ribbon that allows for users to Cut, Copy, Paste and Clear items.
Cut - This will remove the currently selected merged area, returning it to a non-merged selection of cells, and place the merged areas settings onto the clipboard
Copy - This will leave the currently selected merged area as it is, and place the merged areas settings onto the clipboard
Paste - When a merged area is selected, this will paste the currently selected clipboard item into the merged area.
Clear - This will remove the currently selected clipboard item for the clipboard.
The other component of the clipboard is the Clipboard interface itself.
From within this interface, it is possible to select all of the items that have been copied into the clipboard, select the one that is required and then paste this into a merged area, either with the use of the paste button, or double clicking on the item in the clipboard.
Information about the clipboard can also be found in this article.