The family of peppers (Capsicum) includes an enormous diversity of them with all different shapes and level of sharpness. The "sharpness" is caused by the capsaicin alkaloid found in peppers in different quantities.
Chili peppers are popular in the Indian, Indonesian, Mexican and Thai cuisine. Perhaps this is because the spicy chili has a bactericidal and fungicidal effect and helps to better preservation of food in tropical and subtropical countries.