This document introduces different types of language variation, including internal variation which refers to having different ways of expressing the same meaning, varieties which are forms of a language spoken by specific groups that differ noticeably from other groups, dialects which are systematic differences in structural or lexical features between groups within the same language, dialect continua which show gradual transition of features between neighboring dialects, and idiolects which represent the unique way an individual speaks their native language. Extralinguistic factors like region, socioeconomic status, and ethnicity influence the varieties and dialects that emerge.