Some people use the term to refer to the case that contains and protects the motherboard, internal hard drive, memory, and other electronic components of the computer from damage.

System unit.

Explanation:

Some people use the term system unit to refer to the case that contains and protects the motherboard, internal hard drive, memory, and other electronic components of the computer from damage.

A system unit also referred to as chassis or tower can be defined as a hardware case that is typically used as a protective case for the main component or primary devices such as power supply, random access memory (RAM), graphics card, CD-ROM drive, Harddisk drive, motherboard, internal cables, central processing unit (CPU) that makes up a computer system.

Basically, the main purpose of a system unit is to properly house the main components of a computer, serve as an electrical insulator and to prevent them from any form of damage.