I moved and was left a bike from the previous owner. The back tire is flat and I went to pump it up but really have no idea what I'm looking at. The front tire was a schrader valve where I unscrewed the top and pumped it up just like every tire I've ever known. I attached an image of the back tire where I can't seem to find out how to pump it up. The top half of the valve will not unscrew. Is it also a schrader valve with the top just stuck on it?

That looks like the type of valve cap that you can add air to WITH a service station type chuck that you KEEP pressed on while you add air.
It'll come off. Just use a pair of pliers and pull while rotating.

It may have been screwed on too tight and stripped the threads and now just spins?