While researching Cooking with Jane Austen and Friends, I found many recipes that called for lard or suet (the beef alternative). It was often not immediately clear whether or not the authors were talking about straight, diced lard (like the kind used for adding fat and flavor to drier cuts of meat, as in “larding your roast”) or rendered lard, however a trip the local living history museum helped put my questions to rest. A basic rule of thumb when looking at period recipes, if it goes into the food (larding your meat, dicing it for mincemeat, etc.) you are talking about lard straight off the meat, often with tiny bits of meat still attached. If you are using it for frying or in pie crust, basically anywhere you might substitute modern Crisco or solid shortening, use rendered lard.
According to Wikipedia, “Lard is pig fat in both its rendered and unrendered forms. Lard was commonly used in many cuisines as a cooking fat or shortening, or as a spread similar to butter. Its use in contemporary cuisine has diminished; however, many contemporary cooks and bakers favor it over other fats for select uses. The culinary qualities of lard vary somewhat depending on the part of the pig from which the fat was taken and how the lard was processed.