Pepper Essential Oils
As is frequently the case, the English common name (in this case 'Pepper') is used to describe a number of plants which are botanically dissimilar. Brazilian Pepper and Pink (California) Pepper are of the Schinus genus, Green and Black Pepper are the same plant (genus Piper), Szechuan Pepper, a totally different plant much loved in China for the spicy, astringent flavour is a Rutaceae (so related to all citrus plants), and Tasmanian Pepper is a Winteracae.
Green Pepper, Black Pepper (and also White Pepper by the way) are the same plant. The green peppercorn dries out to become black, and then if the husk is removed you have White Pepper.