Final answer:
Adolescence is a transitional period with three phases: early adolescence, middle adolescence, and late adolescence. Each phase is characterized by different developmental changes and focuses. The three phases are physical, cognitive, and psychosocial changes that occur during the transition from childhood to adulthood.
Step-by-step explanation:
Adolescence is a period of transition between childhood and adulthood characterized by significant physical, cognitive, and psychosocial changes. Most psychologists agree on three phases of adolescence: early adolescence, middle adolescence, and late adolescence. In early adolescence, teens experience rapid physical growth and begin to develop their own personal identity. Middle adolescence is characterized by increased independence and a greater focus on peer relationships. Late adolescence involves further identity exploration and a shift towards future goals and plans.