What is Ammonia?
Ammonia has the chemical formula NH3. It is one part Nitrogen and three parts Hydrogen.
What is it Used for?
Ammonia is predominantly used as fertilizer and as a feed-stock for other chemicals.
How is it Made?
Ammonia has historically been made from Coal, Heavy Hydrocarbons or Natural Gas. Most modern Ammonia projects utilize Natural Gas as the feed-stock. An example of a typical process is shown below (reference Kirk-Othmer, Encyclopedia of Chemical Technology, Volume 2, Page 488)
Essentially Methane is combined with Water to make Carbon Dioxide and Hydrogen. The Hydrogen is then combined with Nitrogen to make Ammonia.
You can find more information at this summary on the US EIA website.