Motherboard, graphic card, CPU
Why is the motherboard important?
The motherboard allows all parts of your computer to receive power and communicate with one another. A motherboard by itself is useless, but a computer has to have one to operate. The motherboard's main job is to hold the computer's microprocessor chip and let everything else connect to it. Everything that runs the computer or enhances it's performance is either part of the motherboard or plugs into it via a slot or port.
Why is the graphics card important?
The images you see on your monitor are made up of tiny dots called pixels. At most common resolution settings, a screen displays over a million pixels, and the computer has to decide what to do with every one in order to create an image.
Why is the CPU important?
The CPU is the brains of the computer where all the calculations take place. In terms of computing system, the CPU is the most important element of a computer system.