PvP stands for Player versus Player. On Vox Populi PvP is available in multiple forms for those who appreciate it, and suppressed in some ways as well for pacifists.
Where PvP Can and Cannot OccurEdit
In the Survival World, PvP is enabled in the Wilderness, which means that anyone who wanders outside of a town or other protected region is instantly in a PvP active area and can be attacked by other players. However, creating a town or staying within one's borders prevents PvP in Survival.
In the Skylands , PvP is disabled, and there are no locations where players can battle.
In the Nether, PvP is enabled everywhere and there are no protected regions.