A kayak is a type of small human-powered boat. It was originally developed by the indigenous peoples of the Arctic regions of North America and Greenland commonly known as the Eskimo. The word "kayak" originally meant "man's boat". Construction originally was a wooden frame covered by an animal skin such as seal skin. These original kayaks were used to hunt on the open waters of the Arctic Ocean.

A kayak is typically propelled with a double-ended paddle. The user or paddler sits down in the kayak with their feet forward. The top of the kayak is covered with a deck. The paddler sits in a hole in the cockpit which may be sealed off with a spray skirt (or spraydeck). This makes it possible that should the kayak become inverted (capsize) the kayak will not fill with water, and the paddler , with skill, can right the kayak again without taking on water. This manoeuvre is known as an Eskimo Roll.

In modern times kayaks have been further developed into several types including: whitewater, sea kayaks, flat-water racing, polo-kayak and recreational. These types may also be subdivided. Modern kayaks are made of plastic, fiberglass, kevlar, or wood. They come in one and two person models. Recently some sit-on-top boats have been developed and also called kayaks and propelled with a double-ended paddle.

A special type of kayak is the folding kayak, the direct descendant of the original Eskimo kayak. A "folder" is a kayak that uses a collapsible frame, of wood, aluminium or plastic, or a combination thereof, and a skin, of some sort of water-resistant and tough fabric. Many types have integral air sponsons, inside the hull, making the kayaks virtually unsinkable.

The classic manufacturer of the folding kayak is Klepper, a company in Rosenheim, Germany, which started manufacture of their "faltboot" in 1906. Their Aerius II model was introduced in 1951 and is still in production 2003. In 1956 a Dr Lindemann crossed the Atlantic in a Klepper Aerius II, a proof of the folding kayaks integrity and seaworthiness!

There are about ten folding kayak manufactures today, mostly in the Western World.In Addition to Klepper the most well-known brands today are Feathercraft, Folbot, Long Haul, Nautiraid and Pouch. Long Haul kayaks are virtually identical to Kleppers, so a Klepper frame can be used with a Long Haul skin, or vice versa.

Folders are known for their durability and longevity: The Klepper Aerius I (a single-seater) have successfully been used for white-water kayaking, due to its durability and excellent manouvrability, while many Kleppers have been in frequent use for more than 20 years.