The document discusses different types of letters and their key components. It describes formal and informal letters, as well as different styles of letter writing such as block, semi-block, and modified block. The main parts of a letter are outlined as the letterhead, date, inside address, greeting, title, body paragraphs, complimentary close, and signature. Examples of formal letters include cover letters, resumes, follow-up letters, and references. Informal letters include apologies, complaints, and invitations. The key difference between a hard letter and soft letter is whether it exists in printed or electronic form, and the difference between a letter and application is that a letter responds to someone while an application applies for something in a summarized