Floating shelves are shelves that aren't part of a structure like a cupboard or bookcase, but attach to the walls anywhere you want them or stand free in some other fashion. Floating shelves come in glass, wood, plastic, or metal and in different colours and sizes.
Some floating shelves look like little open boxes that you can stack attractively. Others are more utilitarian, being shelves custom sized for your walls. Some floating shelves have a mirror finish.