Simply an e-motion (energy in motion) just like all other phenomena that arise through the body floating above the natural human undercurrent of peace. As with all energies in motion it comes and goes. Some idiots a while ago figured they'd screw with mankind and make them think that a certain emotion was better than all the others. I mean really come on guys how stupid did they think people we were? Oh wait.
Muskrat: Hey Ravi are you happy? I'm sort of sad because my muskrat jelly just got stolen.
Ravi: Dude man, you can't define your emotions just follow Buddha's teachings bro you'll realize your true peaceful nature eventually.