USB stands for universal serial bus.
A bus is a collection of wires which run in a strapped manner connecting various devices in the inside of a CPU of a computer. If you open up a CPU of a computer you will be able to see the Buses.
USB 2.0 is an external interface which is used to connect plug and play devices like iPods, mp3 players, pen drives etc. By plug and play it means that the computer need not be powered on and off every time the devices are connected.
The Number “2.0“indicates the version of the USB.
USB 2.0 is very much faster than USB 1.1.
USB 1.1 has a speed of 12 megabits per second (mbps), whereas USB 2.0 has the speed of 480 megabits per second (mbps).