Fauna is a collective term for animal life. The corresponding term for plants is flora. Technically, the proper term for fauna plus flora is biota, but fauna is often used instead. In zoology and paleontology the term is often used to refer to the typical collection of animals (and sometimes plants) found in a specific time and/or place -- e.g. the 'Sonoran Desert fauna' or the 'Burgess shale fauna'.
Paleontologists sometimes refer to a sequence of 80 or so faunal stages.
Fauna is also an alternate name for Bona Dea, Ops, Terra and Tellus, ancient Roman goddesses. The name Marica is also used.