This document discusses formal and informal language and how it depends on audience and purpose. It explains that formal language is used in school and when writing to unknown people, avoiding contractions and using proper vocabulary and grammar. Standard English should be used in most school writing and unknown audiences to communicate formally. The audience is who is listening or reading, and the purpose is the reason for communicating - to entertain, inform, instruct, persuade or explain - which determines whether language is formal or informal.