A balloon is different from an airship. An airship is a floating aircraft that has an engine and can change its direction of movement. A balloon has no engine and has no way to change its direction of movement (except up and down). A balloon travels by moving with the wind.
The bottom of the balloon is called the "basket" where people can sit or stand.
The top of a balloon is a big cloth bag called the "envelope".
Kinds of balloon aircraft change
There are three kinds of balloon aircraft:
- Hot air balloons stay in the sky by making the air inside the envelope hot. Making the air hot makes the air spread out (have lower density). Hot air balloons are the most common kind of balloon aircraft. People sometimes say "hot air balloon" to mean any kind of balloon aircraft. But this is not exactly correct.
- Gas balloons are not hot. Gas balloons have gas of low density in their envelopes. Examples of the gas used in gas balloons are helium and hydrogen.
- Rozière balloons are like both hot air balloons and gas balloons. Part of the envelope has hot air in it. Part of the envelope has a gas that's not hot in it. Rozière balloons can fly very far. Rozière balloons have flown around the world without stopping.