This server is called Minescape and it feels like someone turned Minecraft into an MMO. When you play here you focus on skills quests and combat instead of just regular survival.
There is a big focus on progression and a player driven economy. Stuff is not super easy on purpose. Combat and leveling are harder than normal Minecraft so it feels more like an MMO that you stick with for a long time instead of a quick game.
You have to use a custom client mod to join. The client adds special UI and mechanics and it helps stop cheating and abuse. The server actually needs it for the custom content so you cannot play without it. The mod is downloaded from their site and a lot of players already use it.
The people running Minescape say they are a small team and they are still building and improving things. They want feedback and questions from players who try it. The whole idea is to make a fun long term MMO style world inside Minecraft where the players shape the world over time.
