xterm is a linux terminal for a graphical user interface. it is basically the same.
From the Wiki (under other resources: youtube channel) How to use the webui (including setting up and starting a vanilla server: https://www.youtube.com/watch?v=9qIacEjo88M
Minecraft server restart: Auto restart server - #3 by Misiopysio
From the wiki, on installing the webUI:
When creating minecraft servers, it is required to use an unprivileged user to create and manage Minecraft servers. For most distros, this will be with the adduser username command. The password you set during user creation will also be the password used for the web-ui.
You should never use root for anything other than updating system (and the MineOS WebUI).