Cycle computers are essentially one of two types; the simple "how far, how fast, how long?" type, or the more complex, serious training aid. The Edge 500 is one of the latter and is consequently more expensive. It uses GPS to record actual position throughout your ride, as well as the other data displayed by the simpler devices, and stores all of the information in its internal memory. The stored data can be uploaded to a computer for analysis, and the route cycled can be shown as a map display (with Google maps an alternative). The rider may designate a stored route as a 'course'. The rider may then select a course. and race against a 'phantom competitor' over the course to improve his previous efforts. The computer detects when the rider is 'on course' and displays 'distance behind (ahead) and time behind (ahead). The information displayed can be selected by the rider. The bundle being reviewed also comes with a heart rate detector and a cadence (pedal rate) detector, so you can really push yourself to the limit! If want to enjoy your cycling and also want to use it to improve your fitness then this is a very useful gadget to have. I can recommnd it.