What does oyster perpetual mean?

Oyster Perpetual is a term used by Rolex to describe its line of watches that are both waterproof and self-winding. The "Oyster" part refers to the unique waterproof case design that uses a screw-down crown and case back to ensure water resistance, while the "Perpetual" part refers to the self-winding mechanism that automatically winds the watch as it is worn. The combination of these two features makes the Oyster Perpetual watches not only highly durable and reliable, but also convenient as they do not require manual winding. The Oyster Perpetual series includes a variety of models, such as the Datejust, Submariner, and the iconic Rolex GMT-Master II.