Parts inside a Computer case
The motherboard is the computer’s main circuit board. It’s a thin plate that holds the CPU, memory, connectors for the hard drive and optical drives, expansion cards to control the video and audio, and connections to your computer’s ports (such as USB ports). The motherboard connects directly or indirectly to every part of the computer.
The central processing unit (CPU), also called a processor, is located inside thecomputer case on the motherboard. It is sometimes called the brain of the computer, and its job is to carry out commands. Whenever you press a key, click the mouse, or start an application, you’re sending instructions to the CPU.