Input devices are used to enter data and instructions into a computer, while output devices are used to display the results of the computer's processing.
Input devices can be anything from keyboards and mice to scanners and microphones. These devices allow users to enter data into the computer, such as text, images, and audio.
Output devices are used to display the results of the computer's processing. This includes monitors, printers, and speakers. Monitors are used to display text and graphics, while printers are used to produce physical copies of documents. Speakers are used to play audio.
Input and output devices are necessary for a computer to be able to interact with the user. Without these devices, a computer would be unable to take input from the user or provide output.