Vanilla :

The original Terraria server software, intact and unmodified. Due to a lack of configuration, the Vanilla server is not recommended despite its official nature.

tModLoader :

tModLoader is an open-source extension that allows mod support on a server. The possibilities are vast, but the extension must also be installed on each client. It is therefore not possible to host Vanilla players on a TML server.

1. To do this, first connect to the lobby and then to the game server with your Terraria account.
2. Now open the command prompt from the options in the lobby: Options>Persistent server>Execute a command
3. In the command prompt window, enter the command that you want the server to execute, then validate. For example, try "midnight" to see the night fall in the game.
4. You will find the list of console commands on this page: https://terraria.gamepedia.com/Server#List_of_console_commands

When a server update is available, you are notified directly from the lobby activity logs.

To update your server, you will first need to create a new dedicated server on RomStation. Your new server will indeed be created by default in its most recent version.

Then all you need to do is import the data from your old server. So start by stopping your two servers from the lobby options: Options>Persistent server>Stop the server

From the old server lobby, open the file manager (FTP client): Options>Persistent server>Open the file manager

In FileZilla, copy locally this directory "/terraria/Worlds". From the new server lobby, open the file manager to transfer the previously copied directory. If you customized the "/terraria/serverconfig.txt" file, manually reproduce your changes.

Make sure that the data are correctly transferred before removing the obsolete server. And don't forget to restart the stopped server.