[Landain]

Engage in PvE and you earn XP toward level. As you level up you acquire new skills, weapons and armor.

Engage in PvP you gain Rank. As you go up in rank you acquire new skills.

Engage in only one PvE or PvP and the game is boring. You must engage in both in order to fully develop your character.

I have seen no verbage from Webzen about earning "Command Rank" as in PS for leading squads or platoons. So far, rank and status are integral to your guilds/outfits/clans.