When meats or vegetables are sautéed, seared or roasted, they leave behind browned bits stuck to the bottom of the pan. These browned bits can contain an amazing amount of flavoring and are often used to enhance the dish being cooked (say, a ragu, soup or stew) or are later turned into a gravy, glaze or sauce to serve with the finished dish.
Removing that flavoring from the base of a pan and incorporating it into a sauce is called deglazing. To deglaze a pan (see video at left), first remove the cooked meat or vegetables, along with any extra fat. Add a little liquid to the pan to loosen the browned bits; acids such as wine are often used, as are broth or water, even fruit juice. Use a wooden spoon or spatula to dislodge the bits, then use this base as desired in the finished dish.
Make sure that the bits stuck to the bottom of the pan are browned and not actually burnt (black and crusty, they will smell bitter and charred), and be aware that it's harder to get a good deglaze from a nonstick pan because the bits don't really have anything to stick to.
Read more: Gravy is gravy, but sauces are special.