A play, or stageplay, is a form of literature written by a playwright, almost always consisting of dialogue between fictional character, intended for theatrical performance rather than reading. The term is often used in contrast to "musical," which refers to a play with a lot of music and singing.
Many people (especially scholars) read plays for pleasure, or study them in an academic manner. There are rare dramatists, notably George Bernard Shaw, who have had little preference whether their plays were performed or read. So, the term "play" can refer to both the written works of playwrights and to their complete theatrical performance.
Richard Monette, who held the longest tenure of Artistic Director at the Stratford Shakespeare Festival (1994-2007), said that plays on the shelf are literature, whereas plays on the stage are theatre.