WAP and its associated markup languageWML are essentially cut-down versions of HTTP and HTML, reworked for use in mobile phones.
Although useful, WAP and WML are very limited (as is a 5x5cm mobile phone LCD), and are widely considered to be an interim technology that will be superseded as the new generation of 3G mobile devices start to appear in 2-3 years time. That said, WAP is a good stepping stone technology, and many companies are developing around it.