What is the five act structure of a play?

A Shakespearean play has five acts, as did most of the plays written in his time. The division into acts was needed so that there would be opportunities to change the candles when the play was performed indoors; when the play was performed outdoors there were no intermissions. The crisis or turning point of Shakespeare's plays often comes in Act III, especially in Act III Scene 1. So the first two acts give the setup, the crisis comes in Act III and it works its way to the conclusion at the end of Act V. But this is not always the case. For example, in A Midsummer Night's Dream, the conclusion is at the end of Act IV and Act V is by way of an epilogue.