Yes this is unopened :) A tray puzzle is a puzzle your child fits together in a tray instead of dumping the pieces out and putting them together on a table. Hope that helps.
Ok, look at the picture. The edge of the picture is the part of the tray that shows when the puzzle is put together. When you dump out the puzzle pieces the tray has the outline of the puzzle piece. You follow the colors on the side and the outline on the inside to put the puzzle together. These are for young children, probably start at about the same time you would start preschool, so maybe about 3 or 4. It is a teaching puzzle. It teaches hand eye coordination, matching colors and shapes and patience. If you have any more questions don't hesitate to ask.