An expansion or extension of the Serial bus from the motherboard.
One of the better ideas that has evolved over the years. Introduced in the mid
90's it did not catch on because no one had any use for it. The first devices to
actually use the USB were keyboards and mice. Now you can connect external usb CD/DVD Rom
drives, external usb hard drives, joy sticks, Web cams, and network cards. More to come
believe me.
A extremely convenient device, unfortunately most computers only have one or two
ports to connect to. You can "chain" some devices together, some monitors have a
input port and a output port, you can plug in your keyboard to the monitor and
the mouse in to the keyboard, cuts down on the clutter on the desktop.
If you only have one or two ports you can add ports with an expansion device, a
hub, these can have up to eight more ports, I would suggest you get a powered
hub if you go more than four ports, add a cd/dvd rom, hard drive, or go further
than six feet from the port with your cable .
You can also add an internal expansion device to a desk top computer if you have
an empty slot to increase your ports or to bring the ports to the front of the
computer for conveyance.
The new kid on the block is USB 3, usb 3 is ten times
as fast as USB 2. One of the reasons it is faster is the use of duplex, where
the usb controller and device can transmit and received at the same time.
Another feature of usb 3 is the power that the port will supply, maximum power
for a usb 2 port was 1.5 volts where as the usb 3 port can supply up to 5 volts.
This is enough to power an external hard drive, where with usb 2 some external
hard drives needed a separate power supply.
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