I am certain he meant Djinn, which is similar to a (or even a certain type of) Genie. I am not sure the actually myth behind them, but I've heard various stories. Djinn are said to be a type of demon in some instances. They usually have a worse reputation then Genies, and have almost limitless powers. Though this could all just be pop culture ideas, from movies, games, etc.
Wikipedia, or just google it.
As far as formulas, from experience and from hearing other people's stories, it is best to find the ingredients and directions and make the potion, or whatever it may be, yourself. I am fairly certain you can find a free formula to make your own Djinn concoction online somewhere, or in various spell books. If I do stumble across a promising one, I'll post it here.