Range is, simply, the distance at which a character can reasonably attack. The units for range are, in order from least to greatest, meters, kilometers, AUs, and light-years. Beyond this, range is measured in the universal scales outlined in the Cantor system page.
Bear in mind, range is not a measurement of how far a character can theoretically attack or otherwise influence something. An energy beam that continues on infinitely is useless if the character cannot aim at something infinitely far away. Because of this, only ranges a character can effectively fight at should be listed. In addition, ranges that are far greater than normal due to some quirk of the attack should be noted as such, rather than presented as the base range.