Answer:
There are three USB versions, which we'll describe momentarily. Each USB version operates at its own theoretical speed (maximum data transfer rate under ideal conditions). The term data transfer simply means moving data to a different location (say, from a hard drive to a floppy diskette), and data transfer rate indicates the quantity of data that moves from one place to another in a given amount of time. For example, if it takes one second to transfer a 2MB image file from one location on your PC's hard drive to another, the data transfer rate is 2MBps (megabytes per second). In contrast, dial-up modem speeds operate at rates that reach only 56Kbps (kilobits per second).
The original version of the USB standard is USB 1.0, which operates at a theoretical speed of 1.5Mbps (megabits per second). Next came USB 1.1, with a theoretical speed of 12Mbps. Finally, the most recent version of the standard is USB 2.0, with a theoretical speed of 480Mbps, which is 40 times faster than USB 1.1. This is easy enough to follow, but some manufacturers insist on labeling USB products with names, such as "basic speed," "low speed," "full speed," and "Hi-Speed," sometimes without indicating what version (1.0, 1.1, or 2.0) the product actually uses.
Recently, there has been additional confusion about what different USB labels mean. The confusion came about mainly because the USB-IF (USB Implementers Forum, www.usb.org), the non-profit organization that oversees development of the USB standard, revised its recommendations about how the USB versions should be named. The USB-IF prefers that manufacturers don't label products "USB 1.0," "USB 1.1," "USB 2.0," or any of the names mentioned above. Instead, the USB-IF recommends using simply "USB" for devices using version 1.0 or 1.1 and "Hi-Speed USB" for devices using version 2.0.
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