Poster frame and play stop toggle within the project panel appeared and I would like to remove it

The attached image shows the additional element that appeared in the project pannel. When I'm working on a single monitor, it takes up a lil too much space for my comfort. I'm not sure of the intended function, what it's called, or how it got there. I believe I somehow accidentally activated it as it is not in all of my projects. 

Can someone assist me in removing it?