“Single Player is a separate server where you can fully enjoy the world of Dysterra yourself. Before playing in the Official Server, you can control settings just for yourself without any disruptions from other players in Single Player. Also, you can start a new or continue game whenever you want from where you stopped. Please note that your gameplay in Single Player might be delayed if you have a few more softwares running behind on your PC. […] Official Server is the world where you should survive competing against other survivors. You can create a character depending on your current region and also it’s easy to check the server where you have already created a character through the icon on the left.”
Content retrieved from: https://massivelyop.com/2021/07/12/kakao-games-survival-sandbox-dysterra-has-begun-global-beta-testing/.