In Puck's final speech in Shakespeare's A Midsummer Night's Dream, he turns and talks to the audience. What is it called when the actors interact...

There are two answers to this question. One has to do with how a play is written and the other with how a play is performed.

Puck’s final speech is an epilogue. In classical theatre epilogues are speeches that wrap up the action and are often addressed to the audience. So if you are looking at how the play is written, Puck’s speech would be an epilogue addressed to the audience.

The performance technique that you are referring to is called “breaking the fourth wall.” In most theatre the actors act as though the audience isn’t there, as though there is a wall between them and the audience. They don’t make eye contact with or speak to the audience. But sometimes, often when an actor is alone on stage, they break the fourth wall and talk directly to the audience. That is how Puck’s epilogue is performed: spoken directly to the audience.