There are two kinds of Pickled Pork: that pickled in vinegar, and Sweet Pickle pork.
Pork pieces you buy in jars are in a Vinegar Pickle. You can buy jars of pickled pork rind that are very different from the crunchy ones sold as a snack. They are literally just pieces of soft skin pickled in vinegar. They are best enjoyed cold.
You can also buy jars of pickled pork lips.
Most commercially-sold Pickled Pork Hocks in jars are already cooked, and packed in a strong vinegar solution, so that no refrigeration is needed, even after opening. They are sold on the counters at some bars, by the piece. They can be eaten as is.
Both the lips and the hocks are popular among Mexicans.
Sweet Pickled Pork
Sweet Pickled Pork is not the same as pig parts in a jar. It is more similar to corned beef and beef brisket. Examples include Cottage Roll and Peameal Bacon.
The pork is cured with a brine instead of a vinegar. There are many different recipes for the brining. Some add spices, some add sugar, some add saltpetre or Prague powders to pinken the meat and help ensure no botulism. Some use commercial products instead such as Tender-Quick by Morton and just mix with water. Commercial brines might include sodium erythorbate and sodium nitrate.
The brining process has to be done in a non-reactive vessel (see Pickling,)
Butchers used to have tanks of cold brine solution in which they would do, in the same brine, pork, beef brisket, beef tongue, etc. The brine solution would be made of cold water, pickling salt and a small amount of saltpetre to help the colouring of the meat. The meat would rest in the brine for a few days,
Sweet Pickled Pork needs cooking afterward; it is still raw. You cook by simmering it in water, so it is ideal for crock-pots. Depending on what part of the hog it’s from, you can also bake it. You could for instance have a pickled leg, boned, that you stuffed and baked in the oven, or bake a pickled ham with a brown sugar coating.
Pickled Pork is popular in Germany, where they will pickle entire legs.
In Louisiana, it is called just “pickle meat.”