Gifts are the "skills" in Nobilis. They work pretty much like miracles with one exception. Miracles are flexible and mutable. They can adapt to any situation as deemed so. Gifts cannot.
A gift is "purchased" at character creation and it can be used by a character any time they deem necessary without any need to expend Miracle Points. A single gift can do anything, from a single task to several of them separately, only imagination and the HGs judgment limits it's creation.
Based on the Rulebook, Gifts are described briefly and their creation defined by a chart. Again, only one's imagination limits its design. A Gift can be made to be flashy and work much like a Spell in any regular role playing game, something simple like a transformation, a ability to create items from thin air or even a awesome Sword Attack skill that cuts steel like butter and diamonds like bread. All of this usable anytime for free, if the limitations of the Gift itself don't hinder it.
Gifts have their drawbacks of course. Even though having a gift and be able to use it freely has it's advantages, in order to make the gift you have to spend character points which on their own are very limited. Character points invested in the right Attribute can be a lot more versatile, only that if you exhaust your Miracle Points, you are pretty much a screwed Noble.
As a side note worth of mentioning, Gifts can be used even by Mortals and Anchors alike. If a Noble spends an amount of Miracle Points equal to the cost of the Gift, he can bestow that Miracle to a mortal and that Miracle becomes usable as a Gift permanently. A Noble can always strip the Gift from a Mortal at the cost of more Miracle Points, but rarely that's the case. The Cammorae are known to accept gifts from Nobles as payment for their services and that can be used for plot devices whenever a Noble can't intervene in a matter personally.
A good example of this is the Excrucian gift Midas Mors Mortis. It grants, although temporally, extensive and destructive powers to a single touched Mortal.