An actor many have to be prepared to say a monologue (a speech from a play). If he (or she) is auditioning for a particular play then he will take a scene from that play, e.g. if the play is "Hamlet" a male actor who would like the part of Hamlet might have prepared the famous "To be or not to be..." monologue. The director of the play will then be able to decide whether he is good enough, or whether he might be better in another role. They may give the person who is auditioning some other tests, e.g. improvisation or acting with other people.