What is the purpose of the MagSafe cord

There is no MagSafe cord, there is a MagSafe connector at the end of the cord. It's purpose is to provide a quick disconnect in the event the cord is yanked quickly. Prevents the computer from being dragged from a table to the floor and getting damaged.

Not quite sure just what you want to know about the MagSafe...the primary purpose is to supply power to the MacBook Pro Retina to charge the battery and provide operating power while connected to an AC outlet. The MagSafe connector is designed to permit quick disconnect should the cord be pulled so that the user does not trip or damage the computer.

The Magsafe connector is used instead of a friction-fit connector used on those other computers. It only makes the connection (to allow powering and charging) because of the strength of the magnet in the body of the computer.

As everyone has said, its claim to fame is that if someone trips on the cord, it is supposed to disconnect rather than launching your MacBook into low Earth orbit.