Chilli is a spice from the New World, America. It was only with the discovery of the continent by the Europeans that the chili pepper began to conquer the rest of the world. Chili cultivation in Europe started in Hungary and the Basque country. Even Asian cuisine, associated with the preparation of spicy dishes, managed to do that for centuries without any chilli, just like Europe. Until he chili was brought there by the Europeans in the 15th century.
Chillies are fruits of plants from the Capsicum family, with a sharpness that depends on the amount of capsaïcine. The bell pepper is the mildest pepper, only 0 SHU, the unit for measuring the pungency of chili peppers. The spiciest chili pepper now is over 2 million SHU, much too fiery to be eaten pure.