Deglazing is the technique of adding liquid to a pan to dissolve the browned bits left after searing meat.
Those concentrated browned deposits are commonly called fond; related French culinary terminology also uses sucs. After the meat is removed and excess fat is poured off, a cook adds wine, stock, a spirit, or another suitable liquid to the hot pan. Scraping the bottom dissolves the fond and turns it into the flavorful foundation of a pan sauce, gravy, soup, or jus.
The choice of liquid changes the finished flavor: wine adds acidity, stock reinforces savory depth, and spirits can contribute aroma after the alcohol cooks off. The liquid may be served as-is, enriched with butter or aromatics, thickened with starch, or reduced until concentrated. Deglazing is different from reducing: reduction is the later process of simmering liquid to evaporate water and intensify flavor.