Aircraft Research

Military aircrafts

Fighters

The main role of fighters is destroying enemy aircraft in air-to-air combat, offensive or defensive. Many are fast and highly maneuverable. Escorting bombers or other aircraft is also a common task. They are capable of carrying a variety of weapons, including machine guns, cannons, rockets and guided missiles.
WWII fighters include the Spitfire, the P-51 Mustang and Bf 109. An example of an interceptor would be the MiG-25. An example of a heavy fighter is the Messerschmitt Bf 110. The term "fighter" is also sometimes applied to aircraft that have virtually no air-air capability – for example the A-10 ground-attack aircraft is operated by USAF "Fighter" squadrons.
http://en.wikipedia.org/wiki/Military_aircraft

Bombers

Bombers are normally larger, heavier, and less maneuverable than fighter aircraft. They are capable of carrying large payloads of bombs. Bombers are used almost exclusively for ground attacks and not fast or agile enough to take on enemy fighters head-to-head. A few have a single engine and require one pilot to operate and others have two or more engines and require crews of two or more. A limited number of bombers, such as the B-2 Spirit, have stealth capabilities that keep them from being detected by enemy radar. A WWII bomber would be a B-17 Flying Fortress. Bombers include light bombers, medium bombers, heavy bombers, dive bombers, and torpedo bombers.
http://en.wikipedia.org/wiki/Military_aircraft

Military transport aircraft

Military transport aircraft are primarily used to transport troops and war supplies. Cargo can be attached to pallets, which are easily loaded, secured for flight, and quickly unloaded for delivery. Cargo also may be discharged from flying aircraft on parachutes, eliminating the need for landing. Also included in this category are aerial tankers; these planes can refuel other aircraft while in flight. An example of a transport aircraft is the C-17 Globemaster III. A WWII example would be the C-47. An example of a tanker craft would be the KC-135 Stratotanker.
http://en.wikipedia.org/wiki/Military_aircraft