That is, you taste it immediately, and you don't have to wait on the heat as with cayenne. Green peppercorns are unripe black peppercorns. They are preserved in brine and used in a variety of ways. There is a pink peppercorn that comes from Madagascar that is not related to the above family. It has a sweet taste and is very expensive.
Every good cook needs a pepper mill or two on hand at all times.
These are used for grinding the peppercorns. Freshly ground pepper is so much more pungent than the bottled or tinned variety. Fine grind black pepper from the supermarket starts to lose its potency as soon as the container is opened. In six months time it has hardly any taste at all. Peppercorns keep well in a tightly sealed container kept in a cool place.