Native to south India, black pepper (piper nigrum) has of course been used in Indian cooking for millennia. Before the advent of hot chillies from South America, pepper was the predominant source of all 'heat' in Indian cooking. All pepper comes from the same plant, with black being the most common. Black pepper is derived by drying the green berries. Green peppercorn is either pickled in brine or freeze dried.
White pepper is produced by removing the outer, black, covering and grinding it. While arguments rage, chemically white pepper is hotter than black pepper and is preferred in classical cooking to flavour white sauces for aesthetic reasons.
Used extensively in just about all cuisines, the ground white variety is particularly useful in when you want the pepper to blend into the dish (especially if you want the aesthetic appeal of a pure white or pale sauce) or to sprinkle over any dish you are preparing.