Not to be confused with: Beatmaps.
See also: Ranking Criteria § Mapset.
The difficulty of a beatmap describes the level of skill needed to complete it.
Star rating ranges
From the Ranking Criteria, a star rating of:
The star rating ranges determines which web icon is going to be used on any given beatmap. Following the icon ranges would usually give you a good estimate to achieve a balanced difficulty spread. There are some guidelines (see the Mapset section of the Ranking Criteria) you can follow to improve the difficulty spread of your beatmapset.
See also: Difficulty Naming.