The author explores the definition of gifted and talented through a theoretical lens, an operational lens, with international perspectives, and through research and practice examples. This chapter opens the discussion of what gifted and talented is, with a review of prominent models of intelligence, giftedness, and talent. After a theoretical examination of the question, a discussion of operational definitions of who are gifted and talented follows. This section of the chapter will highlight traditional and non-traditional views and the processes used to identify gifted and talented students for services in the United States, Australia, Ireland, and China. The chapter will conclude with a synthesis of what is known about gifted and talented adults, addressing a review of research studies on eminence, discussion of longitudinal studies on talent search programs, and description of specific programs for gifted and talented adults, such as Mensa International.