A Tag in RadioBOSS is something you can assign to a track to help categorize, search tracks, or use a filter when creating a playlist.
Use the Music Library to batch-assign or remove tags: right-click menu -> Add tags and Remove tags command. Tags can also be edited using the Track Tool or the track information panel in the main window.
The "Add tag" window allows creating new tags and using existing ones. To quickly select one tag and close the window, double-click it.
Removing or renaming a tag does not remove or rename it from the tracks where it was used. To remove or rename a tag, first remove it from all tracks in the Music Library, then, if renaming, create a new tag and assign it to the tracks. You can clean up the tag list for music tracks by using the Tools->Tags cleanup menu command in the Music Library.
More information: