A standard for ensuring security and privacy when using WAP 1.x services (mobile web sites) on wireless devices such as phones.
WTLS uses encryption to ensure that sensitive transactions such as mobile banking are secure and cannot be intercepted.
WTLS is an older standard that applied primarily to WAP 1.x. Newer phones and services default to WAP 2.x, which supports the more-common HTTP and SSL standards used by "full" web browsers and web sites.