There are three basic mantels;
Shelf mantel: A shelf mantel is a free standing shelf mounted on a wall. A shelf mantel stands alone and does not have any legs.
Full surround: A full surround mantel is what people typically envision when thinking of a mantel. It consists of a top shelf, breast board and legs. Though a mantel can be plain, it is usually decorated with crown mouldings, panel moulds and other details.
Cap Mantel: A cap mantel is a shelf mantel that is made to sit on top of masonry. The bottom of the cap mantel is made hollow so as to allow it to sit directly on top of a masonry projection.