This document discusses extroversion and introversion as dimensions of human personality. It defines extroversion as focusing energy on external stimuli like people and activities, while introversion focuses energy internally on ideas and concepts. Extroverts tend to be more social, active, and gain fulfillment from others, while introverts tend to be more quiet, prefer fewer close relationships, and gain fulfillment independently. The document also explores theories on how extroversion and introversion may impact second language acquisition and notes it is a continuum rather than an absolute distinction between people.