Jigsaw puzzle

A jigsaw puzzle is a puzzle with pieces in it. Most people think it is harder than normal puzzles. It is usually used as children's toy.
Variations.
Jigsaw puzzles come in many variations, for example they can vary in number of pieces. Standard puzzles contain from 300 to 1000 pieces. The largest commercially sold puzzle had 32,256 pieces. Versions designed for children come in great variety of puzzle piece sizes. Some puzzles are made double-sided so they contain 2 different puzzles on each side. 
There are also 3D jigsaw puzzles. Most of them are made of wood or styrofoam.
There are many jigsaw games available for computers and mobile devices too. Computers have the advantage of interactivity, for example some companies offer you to make custom puzzles based on your photo sent to them.
There is also the last type of a jigsaw puzzle, it is considered a 3D puzzle but made from a 2D pieces. After you assemble pieces in 2D, you bend and adjust the whole creation to make to 3D model.