In the lesson, the concept of friendship is explored through a playful interaction involving Cookie Monster, highlighting the values of sharing and trust among friends. The discussion elaborates on trust, defining it as the assurance of safety and confidentiality when sharing personal matters, exemplified by the act of entrusting a friend with a lunchbox. The lesson concludes by emphasizing the comfort and familiarity that true friendship brings, ensuring that actions are met with understanding and predictability.