PvM stands for Player Verus Monster and It's one of the two Play Styles. A PvM Player is usually strong versus mobs, but weak vs players (weak in PvP).
Any class can be PvM but some are better than others. An example of a great PvM class is the Mirage Sura, while a Example of a bad PvM class is Archer Assassin.
Stats for PvM players are usually HP, Vs Mob, CON/STR/DEX/INT, % to Slow/Faint/Poison, and Movement/attack speed.
Stones for PvM are usually AC, Miss, Fresh, Death and Mob.