A peripheral is a device connected to a host computer, but not part of it, and is more or less dependent on the host. These are also input/output devices. It expands the host's capabilities, but does not form part of the core computer architecture.
Definition: Any auxiliary device such as a mouse, keyboard, hard drive, etc. that connects to and works with the computer in some way. Usually, the word peripheral is used to refer to a device external to the computer, like a scanner, but the devices located inside the computer case are also technically peripherals. Also Known As: external peripheral, auxiliary component
Examples: "Many of the external peripherals I own, such as my scanner and printer, connect to the peripheral ports on the back of my computer."
There are three different types of peripherals: Input Output Storage
An output peripheral is an external device that provides input and output for the computer. For example RAM has a peripheral output. Some peripherals, such as the external hardrive, provide both input and output for the computer. Usually for every external device there are input and output peripherals. An example of only input peripherals, a keyboard and a mouse are input and peripherals. An example of an output peripherals are hard drives disk. The storage peripherals are also considered to be used to store information on the computer for future use.