Pepper, chili, chile, capsicum & chilli are used interchangeably to describe the plants of the genus Capsicum.
The Scoville Scale
The Scoville Scale is a method for measuring the strength of capsicum in a pepper in Scoville units (SHU), which indicates parts per million of capsaicin, a potent chemical that gives them their fiery sensation and that survives both cooking & freezing.
Apart from the burning sensation, it also triggers the brain to produce endorphins, natural painkillers that promote a sense of well-being. Chillies also decrease the risk of heart disease, reduce inflammation, improve digestion (eg. cayenne for ulcers), maintain bone health (high in calcium), lower cholesterol, boost circulation & burn fat.