What is that symbol?

I'm a newbie with iMovie 10.1.2. In the middle of the pic below, what is that red arrow and little icon (maybe an icon for a clip?)? I've no idea how it got there, its uses, its meaning, or how to get rid of it. (The little icon stays where you see it, relative to the red arrow as though it is attached to the arrow.) The red arrow behaves more or less like a cursor. If I move it to the play head, it likes to with the play head. Unless the playhead is in the gap between clips. Then it can be moved elsewhere. Very strange. Thank you