A word processor is software that allows users to create, edit, and save documents. MS Word is a popular word processor that allows creating documents like letters, reports, and web pages. It has features like mail merge, footnotes, bullets and numbering, and converting documents to HTML format. The menu bar in MS Word includes options for file management, editing text, formatting pages, and viewing documents. Common functions include saving documents, finding and replacing text, setting page layout, and copying formatting between sections.