Joints between panels are generally made waterproof by a gunned in sealant. The most widely specified sealant is low modulus silicone. Silicone has high movement accommodation ability and long life expectancy. Primary seals will have a twin outer seal with a cavity between drained at an appropriate point.
Often used as a synonym for "caulk." The word "sealant" usually means a compound that has greater performance than a caulk, i.e., it can accommodate movement in a joint or crack.
Silicone or other product used for creating a waterproof seal around baths, etc.