Chilies are variable in their heat and pungency and also divulge flavors from fruity, sweet, and flowery to earthy, smoky, fresh, and a tinge of licorice. Chile hotness is scientifically determined by HPLC (High Performance Liquid Chromatography) and loosely correlated to scoville ratings. Hot cultivars c. chinense, are high up to 300,000 scoville units. Other cultivars tone down to 5,000 scoville units. Different chilies have surprising hotness ranges affected by environmental variability as well as stage of maturity when picked. Capsaicin and capsaicinoids account for chile heat levels.

The most pungent part of the pod is the placental tissue, or cross wall, which holds the seeds and produces the capsaicinoids. The pepper pod becomes less pungent from the stem end to the apex. 

*Some information from The Pepper Garden by Dave DeWitt and Dr. Paul W. Bosland, p. 121.