United State Cycling Federating categorys for USCF races. Everybody starts as a Cat 5.After 10 races you can upgrade on experience. To go from Cat 4 to Cat 3, it's based on results, but the officials have some discretion. To go to Cat 2 , again on results, and it gets harde rthe farther you go up.
Essentially Cat 5 is beginners. Cat 4, above begginnners. Cat 3 is where it starts to get fairly serious. Cat 2 riders are basically the strongest local to regional riders, and Cat 1's are elite, at the national team level.