I honestly can't believe you guys have never heard of dota!!!
and I'm laughing at Trinnityy here, hon is based on dota how can you possibly not know it.
In any case, LoL and HoN are both derivations of dota, if you've ever played warcraft3, it's a map thats gained huge popularity. You basically get your hero and items, and have two competing sides - source and sentinel - that try to basically kill the other side first.
The genre is unclear but as far as I know it's a real-time strategy game.
Very fun, you have to try it if you haven't take a look at playing on garena (online play basically).