An aircraft carrier is a warship that provides a mobile airbase, equipped with a full-length flight deck and facilities for carrying, arming, deploying, and recovering aircraft.
Aircraft carriers are typically the flagships of fleet units and they are often used to engage in combat operations by projecting air power ashore. The phrase "aircraft carrier" usually refers to large nuclear-powered warships that embark fixed-wing aircraft; however, other types of craft may also be operated from an aircraft carrier such as helicopters or UAVs.
The term may also refer to surface ships carrying limited air power such as escort carriers (e.g., USS "Langley") or amphibious assault ships (e.g. HMS "Ocean"). In modern navies that no longer possess dedicated carriers, such as the United States Navy and the British Royal Navy in conjunction with allies, aircraft carriers are designated as "commando" ships.
There is no single definition of a carrier air wing. While there is agreement that each major navy uses its own type of carrier air wing, there are also common characteristics that distinguish sea-based aircraft carrier squadrons from land-based aircraft.
The word "carrier" in itself does not refer to a unique type of vessel, but rather describes the function of its air wing. Many smaller navies prefer to use the word "airbase carrier" instead, as a way of distinguishing their smaller vessels from carriers with full-length decks (e.g., USS "Enterprise"). This is because the air wing of carriers is much smaller than their land-based counterparts.
Generally, carriers have better range and velocity capability than most land-based aircraft in their squadrons; however, they may be constrained by poorer short-range ability (due to their size) and possibly by operating limitations (such as limited hangars for aircraft). The U.S. Navy has even chosen to build traditional carriers (the Nimitz class) which are large enough to operate a viable air wing and possess a short-range tactical fighter capability, to accompany capital ships in the littoral zone during limited conflict operations.
Today's carrier air wings are usually attached to either an aircraft carrier or a shore-based establishment. They may consist of any combination of fighters, bombers, helicopters, surface attack aircraft, and electronic warfare planes. An aircraft carrier is a type of warship with the role of carrying and operating aircraft. Aircraft carriers are typically heavily-armed with antiaircraft, anti-ship, and antisubmarine weapons to protect themselves and their air wings against hostile forces. Originally called "carriers" because they were centered on an armored ship that carried airplanes, they are now usually called "aircraft carriers" as well.
Most navies also operate other types of ships which perform similar roles in combat or peacetime - amphibious assault ships carry ground troops into battle; cruisers have long range high speed gunnery capable of engaging other ships; destroyers defend against submarines & surface vessels.
The first aircraft carriers were designed in the early 1900s to deal with the possibility of air attacks taking place on long range ships. They were initially based on existing designs, converted to allow them to carry airplanes and equipped with a flight deck. These prototypes evolved into the first aircraft carriers by the mid-1920s as designs were improved to provide for their mission which involved a primary role of winning battles by destroying opposing fleets and defending against air attacks, as well as continuing to perform their traditional roles of reconnaissance and search and rescue.