Which genus of plants includes chili peppers and bell peppers?

The genus of plants that includes chili peppers and bell peppers is Capsicum.

Capsicum belongs to the nightshade family, Solanaceae, alongside tomatoes, potatoes, and eggplants. Its fruits are botanically berries, although cooks usually treat them as vegetables. Bell peppers and many familiar hot peppers belong to Capsicum annuum, while other cultivated species include Capsicum chinense, Capsicum frutescens, Capsicum baccatum, and Capsicum pubescens.

The genus originated in the Americas, especially regions of Central and South America, and peppers were domesticated thousands of years ago. European explorers carried them to the Old World during the Columbian Exchange, after which they spread rapidly through Africa, Asia, and Europe.

A common mix-up is confusing Capsicum with Piper, the genus that includes black pepper. The two are unrelated: black pepper comes from Piper nigrum, while the heat of chili peppers comes mainly from capsaicin. Bell peppers lack significant capsaicin, which is why they taste sweet rather than hot.