This arrow shows you exactly where you are in the clip. You can control it with your mouse or the arrow keys.

The position of the individual's clip while doing some editing. You can control the arrow either with the arrow or the mouse. http://desktopvideo.about.com/library/glossary/bldef-playhead.htm

The red rectangle in the Timeline that indicates what appears on the Stage at any given time.

A marker within the Timeline that indicates which frame is currently selected.