A letter is a written message from one party to another containing information.

Writing is a medium of communication that represents language through the inscription of signs and symbols. wikipedia.org

Copywriting is the use of words and ideas to promote a person, business, opinion or idea. wikipedia.org

SEO content is any content created with the goal of attracting search engine traffic. wikipedia.org

Proofreading (also proof-reading) is the reading of a galley proof or computer monitor to detect and correct production-errors of text or art. Proofreaders are expected to be consistently accurate by default because they occupy the last stage of typographic production before publication. wikipedia.org

A product description is a structured format of presenting information about a product.

A ghostwriter is a professional writer who is paid to write books, articles, stories, reports, or other texts that are officially credited to another person. wikipedia.org

A blog is a personal journal published on the World Wide Web consisting of discrete entries ("posts") typically displayed in reverse chronological order so the most recent post appears first. wikipedia.org

Professional writing involves the use of clear language to convey information in a way that is easily understood by the intended audience. Individuals who can use language well may be employed as full-time professional writers in a variety of communications-related occupations, such as wikipedia.org