Screwing off Showerhead
You can see the connection because it has a wrap of PTFE (Teflon) tape (just above the blue section). Someone used a pliers on it and boogered it up, but there are flats for an open-end or adjustable wrench. You can see one of them on the lower edge facing the photographer.
Support the pipe nipple as you turn the fitting--don't crank on it or you might damage the nipple or the plumbing in the wall.