Minecraft PvE Servers
On Minecraft PvE servers (Player versus Environment servers) players can fight Minecraft mobs, Witches, Creepers, Zombies... sometimes PvE servers would have PvP disabled, therefore only allowing PvE.
PvE is huge part or Minecraft servers since some resources can only be gained by killing mobs, sometimes it would even make sense to create fully automated farms to farm specific resource.
Most of Minecraft servers have PvE enabled but some servers won't spawn any mobs so it's actually almost impossible to PvE. Other servers would allow players to buy and place spawners that would spawn mobs and allow players to PvE.