CCXML, Call Control XML, is a W3C standard language to control telephony systems (both SIP and PSTN). CCXML can make outbound calls, accept inbound calls, create conferences between calls, start dialogs with callers, and send/receive data using web services (e.g., send billing information to db).
CCXML, Call Control XML, provides a W3C standard language to manipulate phone networks (SIP or PSTN), start dialogs with the caller via the VoiceXML language, and can also send and receive data from outside systems. CCXML includes the ability to make outbound calls, answer inbound calls, create conferences between multiple participants, and handle a range of telephony conditions. CCXML applications are in a "state" at all times, and different events (arriving call, call answered, user hangup, response to a dialog, etc.) drive the application. The official CCXML web site.