USB 3.0: (taken from the ever authoritative Wikipedia ) "USB 3.0 can transfer data at up to 5 Gbit/s (625 MB/s), which is about ten times as fast as the USB 2.0 standard. Manufacturers are recommended to distinguish USB 3.0 connectors from their USB 2.0 counterparts by blue color-coding of the Standard-A receptacles and plugs"
 
I have a 3.0 for my external back up drive, nice feature is it being self powered.