This wonderfully unique seasoning is not related to the Piper nigrum.  The flavor is derived from the outer hulls of the small dried fruit of the szechuan pepper. It is very popular in Chinese and other Asian cuisines.  Described as a flavor that is a combination of pepper, citrus and nutmeg; this is an exciting ingredient.  Found in Five Spice Powder it is also delicious in Hot and Sour Soup.  It is best when ground in a mortar and pestal and passed through a strainer.