In the kitchen, Rendering means to Melt down animal fats (like rendering Suet) to a liquid form or to extract animal fats (like rendering Lard) in a liquid form from animal products. Ultimately, though they may be stored at refrigerated or frozen temperatures, the goal of culinary rendering is to separate pure fats from the rest of the animal product so that they can be made into pure, unadulterated Fats for later use.
Saturated Fats, those that are solid at room temperature, are the ones Rendered, since Un-Saturated Fats are already liquid at room temperatures. Saturated Fats can be rendered from any animal products but are most often Rendered from Beef, Pork, Mutton and Poultry. Rendering, or melting the Fats in meat takes place at temperatures ranging from 111° F (44° C) to 158° F (70° C).
Humans have been Rendering for centuries, primarily to make soap and candles. Early Rendering was done in a kettle over an open fire. The invention of Steam Boilers allowed jacketed kettles which made a better Rendered product. Pressure Cooking was the next major invention in Rendering.