What is an act or a scene?

Answer 1

Acts and Scenes are the chunks into which plays are divided. Acts are the bigger chunks which are subdivided into scenes. Acts are usually separated by something big, like an intermission. In Shakespeare's plays, there are usually five acts of roughly equal size. Often there is no reason why one act cannot be immediately followed by another without anyone knowing that a new act has started. Modern plays usually have two or three acts, although sometimes they have only one (In which case, you cannot have an intermission)

In Moliere's and other French plays, a new scene starts whenever someone new enters or leaves the stage. Sometimes a stage manager will divide a non-French play into "French scenes" because it makes it easy to draw rehearsal schedules. In Shakespeare, a new scene usually means that the location has changed. In modern plays, it is more likely to denote a lapse of time.

Answer 2

An act is a major division within a play, typically consisting of several scenes. A scene is a smaller division within an act where the action takes place in one specific location and time. Together, acts and scenes structure the overall narrative of a play.