Schlauch

A hose is a flexible tube that carries a fluid or gas between parts that move or vibrate relative to each other.

Its flexible wall absorbs movement and vibration while holding the pressure and temperature of the fluid inside, which a rigid pipe could not tolerate at a moving joint.

Hoses carry coolant, fuel, air, and hydraulic fluid in the engine bay and around the chassis. The right hose matches the fluid, the pressure rating, the bore size, and the fittings.