When searching for information about a person, it is useful to know the correct subject term used by indexers. In most cases, it will be the last name of the person, followed by a comma, followed by a first name. However, some authors use pseudonyms or there may be several versions of the name. Using the Names as Subject feature, will enable you to find the correct version.
In this example, a search for Twain indicates, that the correct subject term for Mark Twain is Clemens, Samuel, which is this author's real name.