Introduction to Peripherals and Connections
A peripheral is anything that's plugged into the computer box; it can't function on its own without the computer.
anything going into a computer,
the letter that you type, or
a scanned photograph
Anything sent out
of the computer, for example:
the copy of your letter that's sent to a printer, or
sounds sent from a game program to your speakers
Computers typically have a number of plugs in the back of the computer for plugging in "peripheral" devices.
Parallel, Serial, USB
These are the major types of connections between a computer and a peripheral.
To learn more about USB, compared to the others: