Original: Capsaicin The fruit of most species of Capsicum contains capsaicin (methyl vanillyl nonenamide), a lipophilic chemical that can produce a strong burning sensation in the mouth of the unaccustomed eater.
Simplified: Capsaicin The fruit of most species of Capsicum contains capsaicin. Capsaicin is a chemical that can produce a strong burning sensation in the mouth (and, if not properly digested, anus) of the unaccustomed eater.