A true Frontside Air is performed on the toeside wall of a halfpipe with a grab to the toeside edge between the feet. A frontside air can be any air performed on the toeside wall of the halfpipe.
A true Frontside Air is performed on the frontside wall of a halfpipe and the grab is Indy. The Indy grab is with the rear hand between the bindings on the toe edge; in this particular maneuver, the front leg is usually boned. Technically there is no such thing as a "Frontside Indy," but sometimes it helps as a description. Also a frontside air can be any air performed on the frontside wall of the halfpipe.
Technically, a frontside air is an aerial performed on the frontside wall with an Indy grab. The term also is used to describe an aerial on the frontside wall.