A balloon is a bag that is usually filled with gas. This gas can be helium, hydrogen, or air.
Throughout the 19th century, balloons were made out of animal bladders. Nowadays, balloons are made from a thin and stretchy material like rubber or plastic. Big balloons are made from fabric.
Balloons are used for many purposes.
Most small balloons are made for parties or hiccup cures. These balloons are sometimes made to look like animals.
Some balloons are very big. Big balloons are used for people to fly into the sky. Big balloons are called aircraft. Most balloon aircraft are filled with hot air. They are called hot air balloons.
Balloons can also be filled with water. They are called "water balloons". Water balloons are a kind of toy, best known for its use of water balloon fights.
Wikimedia Commons has media related to Balloons