This document discusses different definitions and characterizations of young adults and adolescents from various sources. It explores how young adults have been defined as those ages 12 to 18 by YALSA, but also discusses broader age ranges from 14 to 25 or 20 to 40 depending on the context. The document also examines how generations like Millennials, Gen Z, and Echo Boomers have been characterized based on their experiences growing up with technology and their personality traits.