Pandavas vs. Kuaravas

I don't completely understand how the feud between the Pandavas and the Kuaravas began in the first place. Was it just the Kuaravas' intense jealousy that led them to act out towards the Pandavas and ultimately go to war with them?

And for that matter were the Kuaravas merely fulfilling their own darma by acting out against the Pandavas (trying to burn them in their home, cheating at dice and then banishing them, etc.) in order to maintain their empire? Or would this have been considered adarma because these were backed by selfish reasons?