There are 3 major classes of airplanes: commercial airplanes, military airplanes and general-aviation airplanes. Commercial airplanes are used to make profit and they carry cargo or passengers. Some of the most famous manufacturers are Boeing and Airbus. This kind of plane can carry up to mare than 500 passengers.
Another big plane-making company is Concorde, which managed to manufacture commercial planes that were able to travel up to double the speed of sound.
There are four kinds of military aircrafts: combat, cargo, training and observation. Combat planes are either fighters or bombers. Fighters are open-air combat planes used in defense or offense, and are able to achieve speeds higher than Mach2. There are some fighters that have ground attacking weapons, too. Examples of fighters are the Panavia Tornado, the Boeing F-15 Eagle or the MiG-29 Fulcrum.
Bombers (examples: Boeing B-52, Boeing B-1, Northrop-Grumman B-2 stealth bomber) are combat planes that attack ground objectives. The B-2 uses modern anti-radar technology so enemy forces could not detect them.
Cargo planes carry other military vehicles or weapons such as artillery, tanks or even smaller aircrafts. Examples of such planes are the Boeing C-17 or Lockheed C-5B. Other cargo airplanes, as the KC-10 or the KC-135 (Boeing), are used as gas stations for other planes.
Military pilots need to be trained properly before they will begin to fly real fighters, bombers or other military aircrafts. Some of these planes are Mentor T-34, T-37 and T-38.
Reconnaissance (or observation) planes are used in specialized spying missions. Lockheed's SR-71 is one of the most modern reconnaissance aircrafts. Modern observation aircrafts fly at speeds higher than Mach3.
General-aviation aircrafts are used for private and noncommercial operations. These aircrafts are used either for pleasure, agriculture, or business planes.