USB Full Form, What is USB?

USB full form Universal Serial Bus.

It is the most common type of computer port used in today's computers. It can be used to connect keyboards, mice, game controllers, printers, scanners, digital cameras, and removable media drives, just to name a few. With the help of a few USB hubs, you can connect up to 127 peripherals to a single USB port and use them all at once (though that would require quite a bit of dexterity).

USB is also faster than older ports, such as serial and parallel ports. The USB 1.1 specification supports data transfer rates of up to 12Mb/sec and USB 2.0 has a maximum transfer rate of 480 Mbps. Though USB was introduced in 1997, the technology didn't really take off until the introduction of the Apple iMac (in late 1998) which used USB ports exclusively. It is somewhat ironic, considering it was created and designed by Intel, Compaq, Digital, and IBM. Over the past few years, it has become a widely-used cross-platform interface for both Macs and PCs.

Description:

USB = Universal Serial Bus, pretty much always. There are other technologies with these letters, but as a practical matter, this is the only one anyone cares about.

Universal means that one connector can be used for (almost) anything. Back in the early 90s, you had a different connector for keyboards/mice (generally “PS/2”), printers (generally “parallel”), modems (generally “serial” or “DB-9/DB-25”), external storage (SCSI or parallel), and so on. USB merged all of these (and more) into one connector, signal type, and communications method.

Serial, as the other answer said, is because data is sent one bit at a time, rather than the 8-wire-wide parallel or 16+-wire SCSI, e.g. less wires means cheaper, lighter, more-flexible cables, longer possible cable runs, and simpler system design.

Bus means the topology. Electrically-speaking, a bus is a wire that many devices can plug into at the same time to send/receive data, as opposed to a point-to-point one, where there can only be two devices talking. Every USB port on your computer can talk to up to 126 other devices (at least in theory) by the means of USB hubs. Previous connectors (such as PS/2 keyboards) had no such expansion--you could plug in exactly ONE keyboard (barring serious hardware trickery).

So there you are. Universal Serial Bus, designed to reduce the number of types of connectors on computers and enable new types of devices.