The French term for jigsaw puzzle is "casse-tete", or "break-head", referring to the imputed difficulty of solving.
Jigsaw puzzles were originally created by painting a picture on a flat, rectangular piece of wood, and then cutting that picture into small pieces with a jigsaw, hence the name. Most modern jigsaw puzzles are made out of cardboard, since they are easier and cheaper to mass produce. An enlarged photograph or printed reproduction of a painting or other 2D artwork is then glued onto the cardboard before cutting. The pieces are punch-cut with complex metal dies.
Typical images found on jigsaw puzzles include scenes from nature, buildings, and repetitive designs. Castles and mountains have long been two of the most favorite subjects. Many people solve jigsaw puzzles as a hobby.
Children's jigsaw puzzles come in a great variety of sizes, rated by the number of pieces. Adult jigsaw puzzles typically come in 500-piece and 1,000-piece sizes, and sometimes in 750 pieces, and occasionally 1,500 or 2,000 pieces. These are not the exact counts, which always slightly exceed these.
The method of cutting pieces varies from puzzle line to puzzle line. Many puzzles are termed "fully-interlocking". This means that adjacent pieces are connecting such that if you move one piece horizontally you move all, preserving the connection. Sometimes the connection is tight enough to pick up a solved part holding one piece.
Some fully-interlocking puzzles have pieces all of a similar shape, with rounded tabs out on opposite ends, with corresponding blanks cut into the intervening sides to receive the tabs of adjacent pieces. Other fully-interlocking puzzles may have tabs and blanks variously arranged on each piece, but they usually have four sides, and the numbers of tabs and blanks thus add up to four.
Some puzzles also have pieces with non-interlocking sides that are usually slightly curved in complex curves. These are actually the easiest puzzles to solve, since fewer other pieces are potential candidates for mating. However, a solved part is easily messed up by accidental shock etc.
The uniform-shaped fully-interlocking puzzles are the most difficult, because the differences in shapes between pieces can be very subtle. Occasionally, some puzzles have bizarre cuts to make solving more interesting.
A few puzzles are made double-sided, so that they can be solved from either side.
Some people glue completed puzzles to a backing for permanent display. This is a fairly rare practice today, but was more common at a time when puzzles were more of a novelty.
There are also three-dimensional jigsaw puzzles. Many of these are made of wood and require the puzzle to be solved in a certain order; some pieces will not fit in if others are already in place. Also common are puzzle boxes: simple three dimensional jigsaw puzzles with a small drawer or box in the center for storage.