Ham, technically speaking, can refer to the thigh and buttock of any animal that is slaughtered for meat. The term is usually restricted to a cut of pork, the haunch of a pig or boar. Although it can be cooked and served fresh, most ham is cured in some fashion.
Varieties include Parma ham or prosciutto di Parma (ham from the city of Parma) and prosciutto (ham in the style of Parma but from elsewhere in Italy). Spain has jamon and serrano. USA country ham includes the world-famous Virginia ham, which is smoked.
Ham is also processed into other meat products such as SPAM luncheon meat.
19th-century United States curing recipe
(From The Household Cyclopedia, 1888)
(This is reproduced, word for word, from the original source with added noted in parentheses. Vinegar is not typically used in ham curing in the present day.)
For each ham of twelve pounds weight: Two pounds of common salt; 2 ounces of saltpetre; 1/4 pound of bay salt (coarse salt, possibly sea salt); 1/4 pound of coarse sugar. This should be reduced to the finest powder. Rub the hams well with it; female hands are not often heavy enough to do this thoroughly. Then place them in a deep pan, and add a wineglassful (1/4 cup or 2 US fl. oz) of good vinegar. Turn the hams every day; for the first three or four days rub them well with the brine; after that time it will suffice to ladle it over the meat with a wooden or iron spoon. They should remain three weeks in the pickle. When taken from it wipe them well, put them in bags of brown paper (Warning: the "brown paper" of a modern grocery sack should not be used in this fashion. The recipe probably refers to very plain, unbleached paper. "Brown paper bags" are made from a variety of unknown pulp sources and may have a variety of inappropriate chemicals.) and then (cold) smoke them with wood smoke for three weeks.
