Au jus is a French culinary term that means "with juice." It is a thin sauce or gravy that is typically made from the natural drippings or juices that come from cooking meat, especially beef, chicken, or lamb. Au jus is a way to bring out more flavor in a dish and is commonly served as an accompaniment to prime rib. It is similar to a broth or gravy and can be used in very similar ways. The key ingredients for making au jus include beef drippings, Worcestershire sauce, and red wine. However, there are many variations of au jus recipes that use different ingredients, such as butter, beef broth, and mushrooms. Au jus can be made with or without beef drippings, making it perfect for pre-made dishes or just when you want a dip for your sandwich. The difference between au jus and gravy is that au jus is a light sauce made with pan drippings, while gravy is thickened using a roux.