Lard is fat from a pig. However good lard is made from not just any ol’ pig fat. It comes from the region around the kidneys. This “leaf lard” as it’s called has the mildest flavor and a nice firm texture, and it’s really the only lard that’s good enough for baking applications. Generally you need to find it at butcher shops or farmers markets and must render it yourself. Fortunately that’s pretty easy to do. Good lard does introduce some piggy flavor, but it’s quite nice I think, even in sweet applications.
How does lard stack up against other fats? Compared to butter lard has practically no moisture in it once it’s rendered. It’s pretty much all fat. That means it’s great in applications where moisture can be a problem (like pies and biscuits). Calorie-wise it has 15% more by weight than butter, but then butter is 15% water, so it’s pretty much even-Steven. If you want to substitute lard for butter in any application, you just use a little less of it and the effect (if not the flavor) is the same. Regarding melting points, lard melts at a slightly lower temperature than butter, around 87 degrees Fahrenheit compared to about 90.
Compositionally, lard like butter is made up of many different types of fat (triglyceride) molecules. See the fats primer for more about that. As I’ve mentioned in previous posts on fats, fats that are saturated tend to be firm at room temperature, those that are unsaturated tend to be liquid. Unsaturated fats, it’s thought, are better for you, said to have the effect of raising the so-called “good cholesterol” in the body.
Butter has unsaturated fats in its triglyceride mix, but it has more saturated fats. Lard is just the reverse, more unsaturated fats than saturated fats, which makes it a “better fat” as the present-day thinking goes. It’s even said that the saturated fats that are present in lard have a neutral effect on the “bad” cholesterol in the body. But who really knows? Splitting hairs over which fats are “better for you” makes no sense at all to me. But I digress.