What kind of exercise is using a sauna? How can it benefit me? Should I use it b4 or after or both when working out?

No real exercise! Although time in a sauna may feel good and relax your muscles, the increasing sweating truly depletes your body of fluid and electrolytes. It would not be a good idea either before or after working out. Better to do it after a great massage or before a nice long evening together. Just remember to rehydrate with water and electrolytes!