CCIR System M was a way of making pictures and sounds go from one place to another through the air.
To do this, the pictures and sounds are turned into special signals that can travel through the air. These signals are sent from a transmitting station to a receiving station.
At the transmitting station, the pictures and sounds go into a special machine that turns them into signals. These signals are then sent to an antenna that sends them out into the air.
At the receiving station, there's another antenna that picks up the signals from the air. The signals go into a machine that changes them back into pictures and sounds that we can see and hear on a TV.
The CCIR System M was used in many countries around the world, including the United States. It was replaced by newer systems like digital and high-definition television.