There are many files, each configuring different settings. Some only apply if you're playing single player mode or running a server instance.
These actually are overrides for the default configuration files which are located farther up in the path:
When playing the game online saves are done on the server in question.
In singleplayer mode the game actually runs a local server instance.
Of note are the following files:
You will see multiple game_backup files, it creates and removes these automatically.
If you wish to backup your private server or singleplayer instance, back up the following folders (and subfolders):