Adolescence typically begins around ages 12-14 and ends around age 18. It is a period of transition between childhood and adulthood marked by continuous physical, emotional, and psychological changes. Some of the main physical changes include deepening of the voice, growth of facial hair, and rapid growth of the body. Teenagers today are interested in fashion, music, electronic devices, and associating with different social groups defined by styles like mods, rockers, punks, and hippies. Each group has distinguishing elements related to music, fashion, and activities.