PVP stands for Player Vs. Player, while PVE stands for Player Vs. Environment. These parameters are used to describe the kind of game environment a player is participating in, especially in an online game. In the case of PVE, the player combats against non-players, or monsters to accomplish his tasks. In the process of playing the game, the player can actually be required to have few 'Player Vs. Player' combats encounter to achieve the victory needed. In PVE, the player fights against a computer-manipulated enemy, which usually takes a long time.
In this scenario, you will need to understand the attacking strategy of the enemy, and combats it win. On the other hand, when it comes to the PVP, you will be fighting against a fellow human being. It will require more application of your intelligence as the human opponent is most likely of higher intelligence than the computer-manipulated enemy. The PVP does not usually take a long time like the PVE.