The clipboard is a section of RAM where your computer stores copied data. This can be a selection of text, an image, a file, or other type of data. It is placed in the clipboard whenever you use the "Copy" command, which is located in the Edit menu of most programs.
Data from the clipboard can be pasted into a document or program using the "Paste" command, which is also located in most programs' Edit menu. For example, an image copied to the clipboard from your photo album may be pasted into an image editing program such as Photoshop. A Web address can be copied to the clipboard from an e-mail and pasted into your Web browser's address field.
Some programs allow you to see what data is stored in the clipboard. For example, the Finder in Mac OS X allows you to choose "Show Clipboard" from the Edit menu. When you copy data to the clipboard, whatever data was already stored in the clipboard is typically replaced by the new data. Because the clipboard data is stored in RAM, it is also deleted when your computer is shut down or restarted.