It's an awful term for what it represents.
It's basically a system that forces airlines to be far more accurate in terms of telling ATC when they will be ready for start. From that, the system will build an ideal departure sequence; and from that output a Target Start Approval Time (having taken into account all sorts of things such as slot times, departure route and wake separations etc) to ATC.
The ATC network will have more accurate data on when flights are departing, as well as other users on the airport. The theory is that all the users who are involved in aircraft/passenger ops at an airport should be arranging their duties around the data from their CDM portal, including things like stand planning and immigration.