The ice maker connection is the water supply line that runs from a home's plumbing to the ice maker. It's usually made of 1/4-inch PVC plastic or copper pipe and is attached to the appliance using a connector that shuts off the water supply if the pressure becomes too great.
The shut-off valve on the connector piece is on the inlet side of the connection and activates automatically, needing no power supply. When the water enters the refrigerator, it hits another valve, controlled by an electric solenoid. If the ice maker needs water, the solenoid triggers the valve, allowing the water in. The valve shuts off until the ice is made and ejected.