Yesterday, Season One started in Sea of Thieves, which is how the game will receive updates in the future. One season will run for three months and offer both events, new shipments, content and other stuff. There's also a Plunder Pass for premium items if you really want to spice things up.
You can get a complete rundown on what to expect over at the official homepage, or even better, introduced by Rare themselves in the video below. There's also a general update with several improvements, and something extra for Xbox Series X players, as Sea of Thieves now supports 120 FPS in 1080p.