There are many different types of balloons. They come in many shapes and sizes depending on their intended purpose - transport, play or even medicine. Here are some of them:
Hot air balloon is an oldest type of flying machine. It has an envelope that holds heated air and, most often, a gondola or a wicker basket underneath it which carries passengers. Hot air is lighter than cold which lifts the balloon.
Gas balloon is filled with a gas that is lighter than air - helium or hydrogen. Different balloons can be gas balloons, and this type has a lot of subtypes.
Cluster balloons are clusters of helium-inflated rubber balloons which also can have gondola or a harness that carries a pilot. Cluster balloons are controlled in flight by jettisoning or deflating balloons or by jettisoning the ballast.
Hopper balloon (or just Hopper) is a small, one-person hot air balloon, very similar to standard hot air balloons but with one seat or a harness. Because of their size, their flights last only 1 to 1.5 hours.
Airship or dirigible is a type of a lighter-than-air steerable balloon that uses engines to move through the air. They can have rigid, semi-rigid and non-rigid bodies.
Toy balloon is a small balloon filled with air or helium used for child play, party decoration, and advertising. These balloons are made of rubber, latex or foil and in many colors.
Balloon helicopter is a type of a toy balloon that has a plastic propeller. This propeller is hollow and leads air through each propeller blade which makes propeller rotate.
Water balloon is a toy balloon filled with water and used as a projectile in play fights.
Solar balloon is a balloon, usually made out of material that is light and black or dark balloon material, that gains buoyancy when the air inside is heated by the sun's radiation.
Fire balloon was a type of balloon used by Japan during World War II. It was a hydrogen balloon which carried bombs.
Research balloons are balloons that are used in scientific research. They carry instruments that do meteorological, atmospheric, astronomic, and military research and are usually unmanned. Some of them were even used on other planets (Vega 1 and Vega 2 on Venus in 1984).
Balloon rocket is a long and narrow toy balloon used to demonstrate physical principles and the functioning of a rocket.
Barrage balloon , or a blimp, is a non-rigid balloon tethered with metal cables, used to defend against aircraft attacks making the approach of airplanes more difficult.
Observation balloon were usually hot air balloons or blimps with a gondola that were used for intelligence gathering and artillery spotting.
Ceiling balloon is a type of meteorological balloon that is used to determine the height of the base of clouds above ground level. They are filled with gas, and its ascent rate is known, so the height of clouds is determined according to the time the balloon needs until it reaches the cloud.
Balloon catheter is a balloon used in medicine. It consists of a soft catheter and a small inflatable balloon at its end. During a catheterization procedure balloon helps passage within the body.
Balloons are also inserted into the esophagus, stomach or uterus, and inflated to alleviate or stop the refractory bleeding.
Angioplasty is a surgical procedure in which very small balloons are inserted into blocked or partially blocked blood vessels near the heart. Balloon, placed like that, is inflated to remove or compress arterial plaque.
Some balloons are used as decoys during the war. They are shaped like tanks or some other real item of military equipment, and its purpose is to deceive the enemy.