This document provides information on letter writing, including the importance, mechanics, parts, and types of letters. It discusses that a letter is a written communication directed to a person or organization. Letter writing remains an essential skill for things like job applications and complaints. The document outlines the key parts of a letter, including the heading, salutation, subject, body, closing, and signature. It also describes the differences between formal letters, which are for professional contexts, and informal letters, which are for personal contexts like friends and family. Formal letters have a more serious tone while informal letters are friendly.