Despite its ubiquity, black pepper is one of the more confusing items in the spice aisle. It's not really a pepper, and before it's processed, it's not actually black. Matters become even more complex when you throw white pepper into the mix. Though the two ingredients look different, taste different, and are used in different applications, they both start as berries from the same plant.
According to The Pioneer Woman, white pepper and black pepper derive from Piper nigrum, a crop native to India. To make black peppercorns, farmers harvest small berries from the plant when they're green and underripe. The berries are then cooked and dried until the outer layer becomes dark and shriveled.
White peppercorns are made from fully ripe berries from the Piper nigrum plant. They're soaked in water and fermented to separate the inner seed from the skin. Only the seed is dried to make white peppercorns, and it comes out looking much paler than its more common counterpart.
These two processing methods draw different flavors from the pepper berries. Black pepper is prized for its bold, floral spice, while white pepper has a more mellow, earthy taste. Black pepper is a standard ingredient in most Western cuisine, while white pepper is popular in many Asian cuisines like Chinese, Vietnamese, and Thai. When white pepper is called for in European recipes, it's usually for aesthetic effect. French chefs often use white pepper in mashed potatoes and creamy sauces to avoid black specks in their food.
Though white pepper and black pepper are different ingredients, you can get away with swapping one for the other in most recipes. The same can't be said for peppercorns and chili peppers like jalapeño and habanero. Here are more facts about the hot peppers in your kitchen.
[h/t The Pioneer Woman]