Basically a hack-n-slash grinder. You get spells, level up, play through dungeons and gear up your character, ect... You can see ghosts of all other players currently online and there is some interaction, but full co-op and pvp is coming soon. You also get to create bots that will invade other players' worlds.
So basicaly a much slimmed down beta version of an MMO with new features and environments becoming available over time. It is 100% free with no premium pay-only content.
If you ever played any of the 'Toy Soldiers' games it's made by the same people.
Still waiting for the co-op though...