A peripheral is "an ancillary device used to put information into and get information out of the computer".[1]
There are three different types of peripherals: input devices, which interact with or send data from the user to the computer (mice, keyboards, etc.), output devices, which provide output to the user from the computer (monitors, printers, etc.), and input/output devices that perform both functions. Touchscreens are an example that combines different devices into a single hardware component that can be used both as an input and output device.
A peripheral device is generally defined as any auxiliary device such as a computer mouse or keyboard that connects to and works with the computer in some way. Other examples of peripherals are image scanners, tape drives, microphones, loudspeakers, webcams, and digital cameras. Many modern devices, such as digital watches, smartphones and tablet computers, have interfaces that allow them to be used as a peripheral by desktop computers, although they are not host-dependent in the same way as other peripheral devices.
Common input peripherals include keyboards, computer mice, graphic tablets, touchscreens, barcode readers, image scanners, microphones, webcams, game controllers, light pens, and digital cameras. Common output peripherals include computer displays, printers, projectors, and computer speakers.
