USB stands for Universal Serial Bus. It is an interface for connecting peripherals to computers. Keyboards, printers and portable media players are some examples of peripherals.
USB was invented to replace serial, parallel and PS/2 ports. Combining all of these ports into one made devices more compatible and easier to use. USB transfers data significantly faster than the ports it replaced. Up to 127 devices may be connected to the same computer through the use of hubs.
There are five versions of USB. USB 1.0 was introduced in January 1996. It wasn't until the release of USB 1.1 in August 1998 that the initial bugs were worked out and the system started to become more popular. USB 2.0 was released in April 2000. USB 3.0 was released in November 2008. The latest version, USB 3.1, was released in January 2013. The data transfer speed increased with each USB version.