What does the ':' Operator do?

I've checked the documentation, and this closest I can see to it being referenced is:

To create a callback in Monkey C, create a Method object. Method objects are a combination of the function and the object instance or module they originate from. You can then call the method using method():
// Handle completion of long
function wakeMeUpBeforeYouGoGo() {
// Do something here
}

// Create a call back with the method method (jinx!)
doLongRunningTask( method( :wakeMeUpBeforeYouGoGo ) );



Can anyone explain what this operator does?