You may see Questline, or Minecraft servers in general as simple Minecraft worlds.  But the technical side of it is quite complex.  First, you must compile the right files to make it run, creating a huge mass of folders that are game resources.  Lots of .jsons, .txts, configs, ect.  Afterwords, the world is inserted, and the .properties file is configured for gamemode, difficulty, ect. and the mods are also injected.  Once done, the whitelist is set up, you enter the usernames of all players.  Once done, you either run it on your computer, which requires ethernet and an enormous amount of storage (plus lags out your pc and your internet) or you could rent a private server from a company.  Ours is in Central America, and we use Scalacube.

For our Dynamap rendering (coming soon) we duplicate and extract this world from the server on a regular basis, and then run it from a bedrock world to a java edition one.  Once done, we put it into a diffrent server (in java) which then uses the java exclusive Dynamap plugin to create a 3D render, projected onto our website.