It's a simple question, more lift/and or more duration = more air passing, basically the wilder the figures the more power but usualy shifts it up the rev range, ie the numbering systemon BD cams is std is BD8 basically every number higher is a bit hairier, so alters power output(when set up properly).
Cam spec dependant they will give different amounts of gain at different rpm's, they can also affect idle low down driving substantially if wild enough.
tabetha