Markup Languages

Markup Languages
A markup language is a system for annotating a text in a way which is syntactically distinguishable from that text. Examples include revision instructions by editors, traditionally written with a blue pencil on authors' manuscripts, typesetting instructions such those found in troff and LaTeX, and structural markers such as XML tags. Markup is typically omitted from the version of the text which is displayed for end-user consumption.
A well-known example of a markup language in widespread use today is HyperText Markup Language (HTML), one of the document formats of the World Wide Web. HTML is an instance of SGML and follows many of the markup conventions used in the publishing industry in the communication of printed work between authors, editors, and printers.

HTML, which stands for Hypertext Markup Language, is the predominant markup language for web pages. It provides a means to create structured documents by denoting structural semantics for text such as headings, paragraphs, lists etc as well as for links, quotes, and other items. It allows images and objects to be embedded and can be used to create interactive forms. It is written in the form of HTML elements consisting of "tags" surrounded by angle brackets within the web page content.

The Extensible Hypertext Markup Language, or XHTML, is a markup language that has the same depth of expression as HTML, but also conforms to XML syntax. XHTML can be thought of as the intersection of HTML and XML in many respects, since it is a reformulation of HTML in XML.

XML (Extensible Markup Language) is a set of rules for encoding documents electronically. XML’s design goals emphasize simplicity, generality, and usability over the Internet. It is a textual data format, with strong support via Unicode for the languages of the world. Although XML’s design focuses on documents, it is widely used for the representation of arbitrary data structures, for example in web services.