The common species of chili peppers are:

Capsicum annuum: which includes many common varieties such as bell peppers, paprika, cayenne, jalapeños, and the chiltepin
Capsicum frutescens: which includes the tabasco and Thai peppers
Capsicum chinense: which includes the hottest peppers such as the naga, habanero, Datil and Scotch bonnet
Capsicum pubescens: which includes the South American rocoto peppers
Capsicum baccatum: which includes the South American aji peppers

Assorted bell pepper fruits from MexicoThough there are only a few commonly used species, there are many cultivars and methods of preparing chili peppers that have different names for culinary use. Green and Red Bell peppers, for example, are the same cultivar of C. annuum; immature peppers being green. In the same species are the jalapeño, the poblano (when dried is referred to as ancho), New Mexico (which is also known as chile Colorado), Anaheim, Serrano, and other cultivars.

The species C. frutescens appears as chiles de árbol, aji, tabasco, cherry peppers, malagueta and others.

Peppers are commonly broken down into three groupings: bell peppers, sweet peppers, and hot peppers. Most popular pepper varieties are seen as falling into one of these categories or as a cross between them.