There are four kinds of jigsaw puzzles represented here 1) Standard: In this case a picture is painted or glued on a backer (usually 1/4" ply) and then cut into pieces. 2) Tray: This is similar to the standard puzzle, except that the puzzle fits into a tray. This kind of puzzle is usually for children and, therefore, usually simple. 3) 3D: For this puzzle the pieces are individually cut and then are fit together to create a 3D figure. 4) Shaped: The outside edge of these puzzles form some kind of shape. These puzzles are usually fairly simple and have thick pieces (1/2" or more), so very often they are freestanding.