Remove "canvas" ? in photoshop

Previously, I didn't have a "background" or canvas (not sure what the correct term is) in photoshop. I would open up files and they would all just float on my desktop. I upgraded recently computers, reinstalled photoshop / creative cloud, and now photoshop has a dark background instead of it being transparent. I know in the past I've turned this feature off, but I can't figure out how to do it now. Can someone help?