Chilli peppers can be broken down into the following five species.
Capsicum annuum: This includes many of the more common varieties such as the bell or sweet pepper, Hot Wax, the Cayenne pepper, the Jalapeño, and the chiltepin pepper.
Capsicum frutescens: This group includes the malagueta, the common tabasco and Thai peppers, piri piri, bird eye and Malawian Kambuzi.
Capsicum chinense: This group includes the hottest peppers of all such as the Ghost Pepper, the Habanero, Moruga scorpion, Datil and the Scotch bonnet
Capsicum pubescens: This group includes the South American rocoto peppers and have hairs on the plant unlike other species.
Capsicum baccatum: This group includes the South American aji peppers.