Screenwriting : Beat sheet and outline by Brian McAndrew

There's no standards committee agreeing on definitions to these terms. I'll venture in and say that a beat sheet is a form of outline. I've seen two different things that might be called beat sheets: one is really just a list of story beats, or sequences. You might put these into an outline form: ACT I BEATS, ACT IIa BEATS, ACT IIb BEATS, ACT II BEATS. Or not. The other sort of beat sheet I've seen is based on a prefigured structure. There's a Blake Snyder Save the Cat Beat Sheet out there. I'm sure you could find a "Hero's Journey" Beat Sheet, and a Syd Field Beat Sheeet. That gives you the various expected beats, "Setup", "Inciting Incident", "Refusal of Call", "Plot Point 1", whatever beats are built into that framework. (Then you just fill in the blanks, and POOF, you have a masterwork!) But as you said, you know what a beat sheet is. I'll just define the relationship as: a beat sheet is a kind of outline.

In TV writing, the beat sheet is just that -- a list of the major beats of the scene. So an act one beat sheet would be: 1. Joe finds a dead body 2. Sarah is targeted as the suspect. 3. Peter confesses to the murder. So those are the important moments (or "beats") you want to hit in Act one. Your outline, on the other hand, would walk you to how you get from 1 --> 2 --> 3 in much more detail. It would fill in not only the important moments to the beats, but some of the little moments and character moments you want to include. When you have been at it a while, you start to know how much story you have just by the beats in your acts.