Q: What does each part do?
Well, each part of a computer has its own significance, similarly like in human beings, each and every part of body has its own significance.
Mouse in a computer is an electronic device which is used to give input using "clicks". This device is usually used from the right hand.
Keyboard is an electronic device which is used to type characters, numbers, text, etc. A keyboard is usually used as a text entry interface. It is mainly used with both the hands.
Monitor is an electronic device which displays the result of an input given by a user using the input devices. Today's monitor technology generally used is LED technology.
Printer is an output device which is used to give output result in the form of prints on a paper. It is generally used to print black'n white prints or coloured prints of a document, image, etc.
Well, now lets talk about the brains of a computer. CPU is the abbreviation used for Central Processing Unit is the main component of a computer. This electronic device is neither an input device nor an output device. A CPU receives signals from input devices, processes it and gives an output signal to output devices. Hence, a CPU is the brains of a computer.