A peripheral is a "device that is used to put information into or get information out of the computer."
There are two different types of peripherals: input devices, used to interact with or send data to the computer (mouse, keyboards, etc.), and output devices, which provide output to the user from the computer (monitors, printers, etc.)
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 new devices such as digital watches, smartphones and tablet computers have interfaces which allow them to be used as a peripheral by a full computer, though they are not host-dependent as other peripheral devices are.