Hotness of chilli peppers is measured in Scoville. The range of chillies is from 0 to 2.2 million Scoville. By comparison, sweet peppers have no heat at 0 SHU, jalapeno about 4,000 SHU, habaneros 350,000 SHU and Bhut Jolokia one million SHU. The world record holder for the hottest chilli is currently Carolina Reaper. SHU is the unit of measurement on the Scoville scale.
The genus Capsicum can be divided into 33 species. Among these are many wild species, which are less cultivated by gardeners and farmers. The main species cultivated are Capsicum annuum, frutescens, baccatum, chinense and Capsicum pubescens. For almost 10,000 years, plants from the Capsicum family have been cultivated for yield. Besides a high yield, the capsaicin content, aroma, size and shape of the chillies play a role in cultivation.
Chillies, chilli peppers and peppers are often eaten fresh or processed into a spice. For salads and cooking, their chilli seeds are removed and cut up for the dish. To preserve the spice, chillies are usually first dried and ground into flakes or powder. Chilli threads are more decorative, but more complex to produce.
Carl von Linné founded the scientific naming of plants that is still used today. In his writing of 1753, he also wrote about the genus Capsicum.
An inaccurate and incomplete summary:
Shrubs, annual or perennial herb. Pubenscense with simple hairs. Stem branched. Leaves simple or paired. With petiole, leaves simple, knife-shaped, flat or notched. Flowers solitary or in small groups on leaf axils or branch forks. Pistils absent. Flowers inclined or erect. Typical, radial flower shape. Pedicel erect or inclined. Perianth bell-shaped to cup-shaped, toothed, sometimes slightly enlarged. Petals white, blue or purple. Bell-shaped, divided in the middle. Fruits are juicy berries, sometimes large, erect, pendulous or opposite. Seeds yellowish, discus shape, embryo in seed in dormancy. About 25 species: all in South America, two or three present in nature worldwide, one species in China.
Today we know that all chillies originally came from America.