Adding wine or other liquid to a pan after searing or browning meat or vegetables to help dissolve and remove the brown bits stuck to the pan. These brown bits are very tasty but can burn and become not-tasty.
Alcohol helps dissolve, but it is usually best to allow some of the alcohol to evaporate. Alcohol will evaporate faster if it is allowed to boil if there aren't other liquids mixed with it. Therefore, it is preferrable to deglaze after the solids and before putting in the sauces.