This document discusses language variation and the different types of language varieties. It defines varieties as forms of language that differ in pronunciation, vocabulary, or grammar between regions, social classes, or functions. The key varieties discussed are standard language, dialects, registers, pidgins, creoles, classical languages, and lingua francas. Standard language is used widely for official purposes, while dialects vary regionally or among social groups. Registers differ based on social or occupational context. Pidgins emerge for communication between groups with no shared language, and creoles develop when pidgins are passed to children as a native language.