ADMIN: System → Custom Variables
This feature can be very helpful when adding custom text to you store. Custom variables are moveable pieces of plain text or HTML content great for adding to transactional emails, or adding constant copy and designs to your store with Static Blocks and CMS pages. By doing so custom text and design can be created once and applied to multiple areas to save the merchant time.
See http://www.magentocommerce.com/knowledge-base/entry/creating-custom-variables for more details