Somehow I've gotten a blank tracked named "Master" in my timeline and can't get rid of it. It stays regardless of what project I'm working on. What is it and how do I get rid of it?
It’s the Audio Master Bus track and you hide/unhide it with the B key or menu item View > Audio Bus Tracks. You probably typed the B key while the timeline had the focus.
This is where you can insert master fades, master panning, and other master control properties. For instance, if you have 10 tracks of audio you'd like to fade at one shot...insert an envelope (V) and insert envelope control points where the fade should occur. All 10 tracks will then fade.