When you open an image that supports layers you will see a layer. When you open an image that does not support layers like a jpg, then it opens as a background layer. In either case it is always a photo and can be edited with all the tools available to you.
Just remember if you want to keep any added layers you must save in a format that supports layers like tiff or psd.
Saving as a jpg will merge the layers and give it a white background any place that was transparent.
Another format that is commonly used is png, when supports transparency but does not support layers.
I hope this helps you or any other user wondering that is reading this.