 Typically, the user interface runs on a desktop PC or workstation and uses a standard graphical user interface, functional process logic that may consist of one or more separate modules running on a workstation or application server, and an RDBMS on a database server or mainframe that contains the computer data storage logic.The middle tier may be multitiered itself (in which case the overall architecture is called an ""n"-tier architecture").In the web development field, three-tier is often used to refer to websites, commonly electronic commerce websites, which are built using three tiers