LoL is introducing the Honor system.

[Kirigaya Kazuto]

Remember when you flamed someone because they did a bad call or they didn't know how to focus? Well, believe it or not, that flame affects the performance of the player in the whole match drastically.
LoL is introducing this system to provide a reward to those players who actually try to make a better community.

More info can be found here:
Introducing Honor! - League of Legends Community

[woopasi]

Thats really interesting, so what does it really do? Like is it used for anything other than saying " oh, this guy is nice" or w/e?
But i really think that if it gives a reward then the community will start getting an improvement that it really need.

[Kirigaya Kazuto]

Rumors says its like getting rep here, everyone that felt you were a good player will gave you honor at the end of the match (Does not apply if its ranked team or party members)
End of season will give you a reward, not 100% sure.