This document discusses business letters, including their definition, types, components, and formats. There are three main formats for business letters: block format, modified block format, and semi-block format. Block format aligns all elements left with a margin. Modified block format indents the return address, date, closing, and signature slightly right of center. Semi-block format indents the first line of each paragraph like the modified block format. The key components of a business letter are the sender's address, date, inside address, subject line, salutation, body, closing, and signature.