What is this giant "Now Playing" window, and how do I kill it?

[sandwich]

When I click the annoying little "hidden until I almost click where it suddenly appears" arrow over the Miniplayer (first attachment), I get this hideously engorged "Now Playing" window. I can't figure out why it even exists. I can't figure out how to kill it in a fire.

Note: I like the Miniplayer. I'm fine with the "Now Playing" toast/popup that momentarily appears when a new track begins. This is neither of those.

[Artem]

It seems you've docked it to screen edge. Just drag the window by it caption to undock. Next, close the window.

[sandwich]

Ahh, thanks! It wouldn't drag away because at some point I had apparently pinned it to its position. I used the right-click controls on the title bar to accomplish the same thing and get rid of it.