Magic

Magic is a metaphysical force which can be used to override the usual laws of nature, for a price. Magic is inherently neutral and can't be split between light or dark, though Blue Fairy said that there's Good Magic.

Price of Magic
A darker aspect of OUT's magical system is that magic always comes with a price. The most famous price is Rumplestiltskin's curse, turning him into an almost heartless monster. His price is the heaviest shown so far, making him childish, excentric and hideous though he lost none of his mental capabilities.

Other prices includes Queen Regina's sacrificing her father to unleash her wrath upon Fairytale Land and creating a void in her soul that she can't fill. The most recent was when Mr. Gold brought magic to our world, which though returned his powers also put a barrier around Storybrooke which prevents him from leaving to find his son.

True Love
"True Love is the only magic powerful enough to break any curse."

- Mr. Gold talking to Emma about True Love

True Love is the series' baseline magic, avaliable to anyone and can be used through a kiss. It's the most powerful form of magic and also the most simple. According to Rumplestiltskin True Love can do anything and break any curse through a kiss.

Rumplestiltskin sought to bottle True Love and used hair from Snow White and Prince Charming to craft a True Love Potion. This potion was kept in Maleficent's belly for protection. Later his Storybrooke counterpart, Mr. Gold, would threw the potion into the wishing well and unleash its magic upon the small town.