Waterproof cases are designed to protect the device against liquid, humidity and general submersion. They are used for outdoor activities like boating, going to the beach or generally near water. They are also useful in the kitchen and anti-sanitary environments.
Waterproof tablet cases are vacuum-sealed to protect against liquid entering. Some cases allow for submersion under water. However, most act like bags to keep the water out and keep the device floating when dropped in water.
Depending on product design, waterproof tablet cases are made of silicone, plastic or other flexible polymer materials. If the material is transparent, the waterproof covering may remain in place during active use.
One minus here is a loss of some functionality. Holes for ports and jacks are typically not accessible as they compromise waterproof-ness.