Forge is a PVP team-combat game, basically the end-state of many MMOs without the level grind to make it to that end-state content. It uses many similar character/class/skill tropes found in MMO games. The combat is action oriented, more like Team Fortress 2. It doesn't rely on "tab targeting" as many other MMOs do. The player must stay active and engaged in the combat to be successful.
GameSpy asked if Forge was the "Post-MMO MMO".