USB (United Serial Bus) is a subset of connecting cables designed to help standardize connectors for many computer peripherals (drives, keyboards, cameras, etc.) and cell phones. USB has the capability to enable the transfer of both power and data, reducing the need for separate cables. In the two decades since its introduction, USB has become the most common consumer interface type in use. Because each end of the USB cable is shaped differently, it is essentially impossible to plug in a USB cable incorrectly. USB cables are generally imprinted with the USB logo facing upwards, an attempt to help users recognize quickly and painlessly understand the correct way to plug in their cables.
Full-size USB cables typically come in two configuration shapes: Type A, a flattened rectangle, is the standard type for devices intended to be plugged in indefinitely (keyboards on desktop computers, for example). Type B, mostly square with two slightly angled corners, is used for "upstream" data transfer (asin, a computer to a printer).
As USB technology improved, 'mini' versions of both types were introduced, which led to the introduction of the even smaller, 5-pin micro-USB cables, now far and away the most common cable for cell phone connection. Over the years, a number of electronics manufacturers have redesigned the USB interface into a configuration intended only for their brand, like the ubiquitous Apple iPod/iPad/iPhone 30-pin plug, featuring both USB and HDMI capabilities.
The newest version of USB, USB 3.0, is the newest USB specification revision. USB 3.0 boasts a transfer speed around ten times faster than the previous USB specification (around 5 GB/second). USB 3.0 is also designed to be backwards compatible with the previous specification, USB 2.0.