Why do I have two desktops?

I have noticed I have two desktops on my computer. It was accidental I found it. I was trying to see the desktop under a page I had opened and when I moved it to the right I guess I went too far and it popped over to another page. It was a different color than the one I use, which is how I even noticed it. Is this second page something that belongs there, or have I done something to create a new one? If I created a new one, how do I get rid of it?