Exif is a format for storing metadata in image files. A table of Exif data is presented in Metadata section of file pages such as this one. The tags are summarized here and described in further detail in the full specification document.
This message labels the author or artist of the work. Usually this means who took the photograph, or who drew the picture. The corresponding value field most commonly contains a single author, however it can contain an ordered (or unordered depending on which metadata standard is used to store the information) list of authors. Sometimes the persons position is prefixed before their name such as "Photographer, John Smith". The exif standard recommends multiple authors be specified by "position, Author 1; position for author 2, Author 2's name" however this doesn't seem to happen in practice very often. If multiple authors are specified using a non-exif standard, then a billeted (or numbered) list is used.
This property can be specified by exif Artist tag, XMP's tiff:Artist, XMP's dc:creator, iptc-iim's 2:80 byline, PNG's author textual chunk, PNG's (unofficial) artist textual chunk. XMP's photoshop:AuthorsPosition and iptc 2:85 byline-title can also affect display of this property.