If you want to explore the game world of DayZ together with your friends, without having your own server you have the choice between the official servers, which are public by default, and the community servers, which are hosted by other users. In both cases, however, you have no influence on which other players can join the server, which mods are used or when the server is online. You can only enjoy these freedoms with your own DayZ server.
If you have a computer with powerful hardware and an excellent Internet connection, you can install and run your own DayZ server on your device. However, as soon as you shut down the PC or the Internet connection is interrupted, the online adventure ends abruptly. Moreover, you cannot run the DayZ client on the same device - so if you want to play along, you need another computer.
If you rent a server from a provider to host a DayZ server instead, you won’t have to worry about aspects such as Internet connection and availability. The functionality of the hardware is guaranteed, and you can focus entirely on setting up and administering the server.