PvE

Player versus environment (PvE) is a type of interactive conflict within a game where players compete against computer controlled opponents. It differs from PvP which is player versus player. These are the two foundational modes of game-play which often drive how players design their Character builds.

PvE builds are typically more versatile with multiple skills but are not optimized for the most competitive combat between players. PvE Characters are often trained in some Professions and usually have less need to use Drugs. Players who start the game casually, usually register a build that is PvE by default.

Meanwhile, PvP builds are elite fighters often with high Luck and higher chance to do critical damage, with mostly combat perks. PvP builds are carefully designed for the most competitive combat, and nearly always use Drugs. This includes Sneak Characters if built properly. Players who do not carefully design a build will not usually end up with a proper PvP build, but a PvE build or a "broken build" at best.

Sources

http://en.wikipedia.org/wiki/Player_versus_player