Fauna means animal life. It is a group term; it means the animal life typical of the time or place. It is a similar term to flora in Botany.
So one might speak of the Eocene fauna as being different from the Miocene fauna. Or, say, the fauna of a particular habitat. The flora and fauna of a savannah differ from those of a rain forest.
Another use of the word is for published lists of animals, such as: