The power catamaran is a boat which has two hulls connected by a large deck area. Each hull has a very narrow beam (width). These hulls, individually, would be very unstable. Paired up with a rigid deck in between, however, the two hulls become a stable platform. Having less wetted surface - thus, less drag - the catamaran is easily driven and tends to slice through waves instead of pounding down on them. Originally a sailboat design, the "cat" is becoming a popular powerboat.

Capacity	4 to 10 people or more.
Power	Catamarans carry two engines - one in or on each hull - and are either gasoline or diesel. Catamarans have either outboard, stern drive or vee drive systems.
Size	16 - 50 feet.
Hull	Usually the hulls are deep vee in design. Some high performance catamarans have as many as six steps (or ventilators) on each hull bottom to further lessen drag (I'll get into the concept of "Drag" in a another article). The most popular hull material is Fiber Reinforced Plastic (FRP), but a few have been made of "cold molded" wood or aluminum.
Trailerable	Yes. However, some of the larger models use a special trailer that tilts the boat so that it will conform to highway width restrictions.
Uses	Great for fishing, watersports and cruising. The high performance (read: "belch-fire") cats really fly!
Limitations	All the engines, generator and other mechanical equipment, must be placed in the two narrow hulls along with sleeping and head (bathroom) facilities, which doesn't allow for much leftover space. Also note that catamarans will tend to lean outboard in a turn, just like big ships do. Most other power boats, however, will generally lean into the turn. In rough seas, you may get some pounding on the bottom of the deck between the two hulls.