Airships, also known as dirigibles or blimps, are a type of transportation that uses gas-filled balloons to achieve flight. They were first invented in the late 19th century and have played a significant role in the history of air travel. The design of an airship consists of a lightweight frame covered in fabric, with an internal structure for the gas-filled envelope that gives it its iconic shape. The most commonly used gas is helium, which is lighter than air and helps the airship to achieve lift.