What is the Scoville scale?
The Scoville scale measures the hotness of a pepper.
A "Scoville Unit" is actually a measure of capsaicin, the chemical that makes a hot pepper hot. Most capsaicin is found in the ribs and seeds of a pepper, which is why seeding a pepper makes it's heat less potent.
You might have noticed a Scoville rating on your bottle of hot sauce. Original
The rating of a bell pepper? Zero -- no heat from this pepper.
(image courtey of wikipedia)