(Pronounced CHA-see) Chassis, more commonly called the computer case, is a metal frame that serves as the structural support for electronic components. Every computer system requires at least one chassis to house the circuit boards and wiring. The chassis also contains slots for expansion boards. If you want to insert more boards than there are slots, you will need an expansion chassis, which provides additional slots.
There are two basic flavors of chassis designs-desktop models and tower models-but there are many variations on these two basic types. Other names for chassis include: tower, case, cabinet or enclosure.