Black pepper is nearly as common in cooking today as salt is. At one time, it was so rare a commodity that peppercorns were actually used as currency. While it can be found in Thailand and Malaysia, it's main roots are in the Malabar coastal region of India. It is the oldest spice known, and the most widely used.
Prior to the 1800's, pepper was a luxury item, only affordable to the royalty and the upper classes. Acquiring it was a major force behind the spice trade. Many a fortune was won and lost on this “black gold.”
There are several varieties of pepper and most come from the Piper nigrum. Don't confuse this with cayenne pepper, though. They aren't related. Cayenne comes from chili peppers, not the fruit of the Piper nigrum. Their heat sources differ as well. Cayenne gets its heat from capsicum, while peppercorns get their heat from piperine.
While pre-ground black pepper is available, I recommend getting a decent pepper mill and buying the pepper corns. There are two good reasons that Mormons, especially, should consider this. First, the flavor is much better. Second, like all spices, peppercorns will remain tasty in food storage much longer than ground pepper will. As ground pepper ages, I find it can take on an unpleasant mustiness.
These come from the not-quite-ripe berries of the Piper nigrum vine. After they've reached full size, they are picked and dried in the sun. Enzymes in the berries cause the skin to turn black during the drying process. It has the strongest in flavor of all peppercorns, and is my favorite.
These are fully mature, red, ripened berries. After harvesting, the outer skin is rubbed off to expose the smooth layer underneath, and then dried and bleached by the sun. They are slightly milder than black pepper and are favored in white sauces because they don't speckle the food.
I use black peppercorns almost exclusively. I appreciate the flavor and don't have a problem with speckled food.
This variety is picked at the same time as black peppercorns, but they aren't allowed to dry. Instead, they are pickled in a vinegar or brine solution. You can find them freeze-dried and dehydrated, but the dehydrated ones have more flavor. The flavor and heat are less pronounced than black peppercorns and they are the least pungent.
This is a mature peppercorn that still has it's outer skin. They are is often difficult to find outside of gourmet shops, and can be very expensive. They are pungent like a black peppercorn, with a slight sweetness.
These are actually unrelated to the black peppercorn. They come from the Baies rose plant and are imported from Madagascar. As a result, they are rather expensive. They are pungent and slightly sweet, but don't have nearly the amount of flavor.
Often called pink peppercorns, which they are not, they aren't related to the black peppercorn or the Baies rose plant. Instead, it's the seed of a plant known as either the Brazilian pepper tree, Christmas berry, or Florida holly, even though it's considered a scourge in that state. I've been told the flavor is more like sweet menthol, but I refuse to eat them. They can cause severe allergic reactions, especially in children, and are toxic when eaten in large quantities. Avoid these.
In many gourmet shops you will find a blend of black, white, green, red, and pink peppercorns under the name of a “five pepper blend.” They are used mostly as a condiment or sprinkled on before serving as much for their decorative quality as their flavor.