A dot com is any Web site intended for business use and, in some usages, it's a term for any kind of Web site. The term is based on the .com that forms the last part of the address for most commercial Web sites. The term is popular in news stories about how the business world is transforming itself to meet the opportunities and competitive challenges posed by the Internet and the World Wide Web. Alternative spellings seen include: dot.com, dot-com, and dotcom. Source: Whatis.com