Morality plays are a type of theatrical 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 century. 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.
However, by the 16th century these plays started to deal with secular topics as medieval theatre started to make the changes that would eventually develop it into Renaissance theatre. As time moved on morality plays more frequently dealt with secular topics, including forms of knowledge (in Nature and The Nature of the Four Elements) questions of good government (Magnificence by John Skelton and Respublica by Nicholas Udall), education (Wit and Science by John Redford, and the two other "wit" plays that followed, The Marriage of Wit and Science and Wit and Wisdom), and sectarian controversies, chiefly in the plays of John Bale.
Morality plays only gradually died out as tastes changed towards the end of the sixteenth century. Throughout his career Shakespeare made references to morality characters and tropes, suggesting that the form was still alive for his audiences, at least in memory, long beyond the period of its textual flowering.
Morality plays were typically written in the vernacular, so as to be more accessible to the common people who watched them. Most can be performed in under ninety minutes.