An MTR, or Motion To Revoke, is a Motion filed by the Prosecutor in the Court of the Judge where you were sentenced. It tells the Court what you are on probation for, when you were put on probation and what you have done or not done that is in violation of the terms and conditions of your probation. Your probation officer notifies the Prosecutor that you have failed to comply with your probation terms using a Violation Report.
When a Prosecutor files an MTR, the Judge will review it and typically sign it. At that point a warrant goes out for your arrest. When you are arrested, you will be taken to jail and held without bond. The term for this "remanded without bond." You will stay in jail until you make bond or appear before the Judge on the MTR.