It's an MMORPG. You basically pick a character, do missions that involve killing monsters, level up, get better equipment. I haven't gotten deep into the story, but you're a mercenary working for the Crimson Blade Mercenaries. There was a prophecy that you have to kill monsters called Fomors to get to a promised land.
Here's a gameplay video, against the tutorial boss:
http://www.youtube.com/v/Wn1Jag4bmdU