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The Wireless Markup Language is WAP’s analogy to HTML used on the WWW. WML is based on the Extensible Markup Language (XML). 

WML uses a deck/card metaphor to specify a service. A card is typically a unit of interaction with the user, that is, either presentation of information or request for information from the user. 

A collection of cards is called a deck, which usually constitutes a service. This approach ensures that a suitable amount of information is displayed to the user simultaneously since inter-page navigation can be avoided to the fullest possible extent.

   Key features of WML include:   
· Variables
· Text formatting features
· Support for images
· Support for soft-buttons
· Navigation control
· Control of browser history
· Support for event handling (for e.g. telephony services)
· Different types of user interactions, e.g. selection lists and input fields

WML can be binary encoded by the WAP Gateway/Proxy in order to save bandwidth in the wireless domain.

WMLScript
WMLScript is based on ECMAScript, the same scripting language that JavaScript is based on. It can be used for enhancing services written in WML in the way that it to some extent adds intelligence to the services, for example procedural logic, loops, conditional expressions, and computational functions.

WMLScript can be used for e.g. validation of user input. Since WML does not provide any mechanisms for achieving this, a round-trip to the server would be needed in order to determine if user input is valid or not if scripting was not available. Access to local functions in a wireless device is another area where WMLScript is used; for example access to telephony related functions. WMLScript does also support WMLScript Libraries. These libraries contain functions that extend the basic WMLScript functionality. This provides a means for future expansion of functions without having to change the core of WMLScript. Just as with WML, WMLScript can be binary encoded by the WAP Gateway/Proxy in order to minimise the amount of data sent over the air.