and pay special attention to the OTC and ScanMaster columns. The OTC listed is a 4000, so if they are offering you a 2000, it's different in that you can only see 2 parameters of data at a time, has an LED display vs an LCD display, and it is more limited in the years/models of cars it supports.
The 2000 is a good basic scanner. If you can get it cheap, it's pretty neat. The chart listed above should pretty much list the differences between the scan tools.... if it's not clear and you have some specific questions, drop me a line and I'll answer them as best I can: