A personal letter is an informal letter written to someone you know on a friendly tone. It should include a reason for writing, exclude information the recipient already knows, and use the right tone and language. The document provides examples of personal letters to a relative and close friend and discusses how the tone can vary depending on the closeness of the relationship. It also covers the typical format of a personal letter, including sender's address, date, salutation/opening, introduction, body, closure, complimentary close, and sign-off. Tips are provided on making the letter interesting through tone, sharing emotions, format and style, and making connections with the recipient.