Pork is all the meat that comes from a pig, and ham is a specific part of the pig. Just like steaks comes from particular parts of a cow, ham comes from a specific place on a pig's body.
All ham is pork, but not all pork is ham. A pig has many different cuts of meat. Ham is sometimes called thigh or rump as that is where the ham comes from. Pork and ham can come from either domesticated or wild pigs.
Another way to tell the difference is to remember that ham is almost always cured and most other cuts of pork are raw. Raw pork can be flavored with a wide variety of seasonings and cooked in a number of different ways. Roasted, smoked and boiled pork are eaten in many countries around the world, although for religious or other reasons, some people refuse to eat pork.
Ham is usually cured and sometimes smoked. It has a unique flavor when compared to other cuts of pork. In the United States as well as in other countries, ham is served at holidays, such as Easter and Christmas.
Although ham is also sometimes called bacon, that cut usually comes from the loin or the side of the pig, sometimes referred to as the pork belly.