WML is a markup language built specifically for communicating across WAP-based networks, and is based upon XML (eXtensible Markup Language). It is at first glance similar to HTML, but is also a much more strictly written language. 
To make it possible for web pages to be read from a WAP-enabled device, WML must be used. The WML coder determines within the code what parts of the web page are viewable to the device. The advantage of the WML language is the fact that, since it is a subset of XML, developer's can easily kill two birds with one stone by building both the web page and wireless device page simultaneously. [DEVSHED]

The major function of WML is:
*Text presentation and layout - WML support text and image, including variety of formating and layout command. ( eg. boldface text )
*Deck and Card organization metaphor - all information in WML is organized into collection of cards and decks. Cards are specify one or more units of user interaction ( such as a choice menu, a screen of text or a text entry field). Logically, a user navigates through a WML cards, reviews the content of each, enters requested information, makes choice and moves to another cards. Cards are grouped into decks. This decks are similar to HTML page, which is identified by URL and is the unit of content transmission per request over network.
*Inter-card navigation and linking - WML support navigation between cards and decks. Also WML handles event in the device, which may used for navigational purposes or to execute scripts. WML also supports anchored links, which we can find it in the HTML too.
*String parameterisation and state management - all WML decks can be parameterised using state model [WAPWML]. Variables can be used in the plcae of strings and are substituted at run-time. 

[DEVSHED] "Introduction to Wireless Access Protocol", W.J. Gilmore, 18-Feb.-2000. 
[WAPWML] "Wireless Application Protocol Wireless Markup Language Specification ver 1.2", WAP Forum, 4-Nov.-1999.