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.