A subject is anything of primary focus for the poster. It could be a musical artist, an album being promoted, an event venue, a movie or TV show, or a musical, film, or cultural festival. Basically, if it is listed on the poster, then it is a potential subject. Do your best to fill out details on the subject including photos. When possible, insert the link to musical artist pages at Discogs and movie pages at Filmogs. This type of crosslinking will help bring exposure to the other sites as well.