USB or Universal Serial Bus is an external bus that supports transfer rates of 12 Mbps, can support 127 devices and supports hot plugging.
Serial Bus) is a new external bus developed by Intel, Compaq, DEC, IBM,
Microsoft, NEC and
USB cables are hot swappable which allows users to connect and disconnect the cable while the computer is on without any physical damage to the cable.
The above illustration is an example of what the end of a USB connector looks like. There are two standards of USB connectors. Type A connectors are found on the computer and or USB hub and Type B connectors are found on the peripheral. All USB cables should only be legally 5m (16ft) max as defined by the USB standard. When exceeding this length or utilizing extensions in the cables data loss will occur.
The below illustration is the slots used for each of the connectors shown in the above illustration
USB 1.0 - The original release of USB support with support of 127 devices transferring 12 Mbps.
USB 1.1 - Very similar to the original release of USB however minor modifications for the hardware and the specifications.
USB 2.0 - USB 2.0 developed by Compaq, Hewlett Packard, Intel, Lucent, Microsoft, NEC and Philips was introduced in 2001 and is capable of supporting a transfer rate of up to 480 Mbps. USB 2.0 is backwards compatible capable of supporting USB 1.0 and 1.1 devices and cables.