As you might have guessed, an Author search looks for particular authors within the catalog. Like a Title search, this search will most often be used for "known item" searches, that is, you know the name of the author you are looking for.
Be aware, that as with subject headings, authors listed in the catalog are listed in a particular way. The more you know of the author's name (e.g. correct spelling and middle initial), the more successful you are likely to be.