INTERCUT: This is often used when showing two or more characters interacting from two separate locations. A telephone call is the most obvious use, but it is also quite handy for parallel action such as the opening of Hitchcock’s
Strangers on a Train.
An excellent example is from Charles Deemers'
PRACTICAL SCREENWRITING (did I mention you should buy this book?):
If we hear and see both parties:
INTERCUT PHONE CONVERSATION - JOE'S BEDROOM / MARY'S BEDROOM
JOE
Did I wake you?
MARY
That's all right.
Sometimes you can do this more efficiently within the context of the story this way:
INT. JOE'S BEDROOM - NIGHT
Joe dials a number.
INT. MARY'S BEDROOM - NIGHT
She answers the phone.
INTERCUT
[and the conversation as before]