If an actor speaks directly to the audience it is called an aside.
If an actor speaks to himself, while only the audience can hear, it is called soliloquy.
The fourth wall is a hypothetical barrier between the actors and the audience. This barrier is broken when an actor interacts with the audience through an aside.
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The actor talks in a musing tone of voice, usually facing diagonally down-stage. He doesn't talk to the audience; he is voicing his thoughts and the audience just 'overhears' them. The name for this is a soliloquy.
A soliloquy
Stage Managers do not generally speak to the audience unless a situation arises and the performance is interrupted (such as a fire or an actor being seriously injured on stage). If a Stage Manager talks to an audience out with this it may be at the request of the director who wished them to introduce the show.
That is called an aside.
It's called an "aside". It is a line that the playwright directs the actor to deliver to the audience, which is called "breaking the fourth wall". Neil Simon's comedy "Fools" is full of asides to the audience.