The morality play is a genre of Medieval and early Tudor theatrical entertainment. In their own time, these plays were known as interludes, a broader term given to dramas with or without a moral. Morality plays are a type of allegory in which the protagonist is met by personifications of various moral attributes who try to prompt him to choose a Godly life over one of evil. The plays were most popular in Europe during the 15th and 16th centuries. Having grown out of the religiously based mystery plays of the Middle Ages, they represented a shift towards a more secular base for European theatre.
Virtual Theatre Useful explanation of Interlude in Renaissance Drama.
McGraw-Hill Good definition of Interlude.