Although it shares some similarities with salt pork and lardons (cubes of fatty bacon), it sounds like lardo is it's own distinct entity.
Lardo is made from the thick layer of fat on the back of a pig (that is to say, fatback!), which is cured with a mixture of salt, herbs, and spices. It's Italian in origin and some of the best is said to come from northern Tuscany where lardo was a primary source of calories during lean times.
According to Ed Behr from The Art of Eating, the only spices traditionally used to make lardo were sea salt, ground black pepper, fresh rosemary, and chopped garlic. During curing, the salt draws moisture from the fat and creates a brine that protects it from air and spoilage. Behr says that lardo can be aged for anywhere from six months to two years, always improving with age.
Lardo cured and sold in great slabs like you see in the picture above. It can be sliced thick and made into a (very hearty) sandwich, but these days, you'll more often see it sliced wafer thin and served as part of an antipasti platter. The texture is described as delicate and creamy while the flavor is slightly sweet and herbaceous.
Now we just need to get our hands on some! Have you ever tasted lardo?