The document discusses the definition and types of letters. It begins by defining a letter as a written or printed communication directed to a person or organization. It then discusses the different types of letters, including personal/informal letters, formal letters, and semi-formal letters. For each type, it provides examples of their purpose and appropriate tone. The document also covers letter formatting, mechanics, and things to remember when writing different types of letters such as salutations, compliments closes, and proofreading. Finally, it distinguishes between personal letters and business letters, providing details on each.