The process of cooking pork, duck, or other fatty meat to melt and release some of its fat is called rendering. The melted fat is collected as a cooking ingredient, while the remaining browned solids may be crisped and eaten.
Rendering can be done slowly over low or moderate heat, either in a pan, oven, or pot. As the fat melts, moisture evaporates and connective tissue separates from the liquid fat. Pork fat rendered from pieces of skin and fatty meat is commonly called lard; rendered duck or goose fat is prized for roasting potatoes and other vegetables.
The term is broader than simply frying. Frying usually cooks food in hot fat, while rendering extracts fat from the food itself. A cook may render bacon before using the crisp pieces, or render duck legs as part of a confit preparation, in which the meat is cooked gently in its own fat.
Temperature control matters because excessive heat can scorch the solids and give the fat a bitter flavor. Properly strained rendered fat can be stored and reused, although its shelf life depends on removing water and food particles.