Main line  - (pressure line) The pipe that runs from the backflow prevention device to the solenoid valves. The main line delivers water to a central location on your yard. On smaller jobs the main line will be not much longer than the width of the house or shorter. This pipe is usually PVC (white pipe) and, unless a master valve is installed, usually contains constant water pressure. Connected by solvent welding.

Lateral  - (poly line) This is the black pipe that runs from the valve to the heads. It is only under pressure while that zone is in operation. Connected with clamps.

Master valve  - An optional valve that keeps water from going to the solenoid valves and main line, unless the controller is calling for system operation. The master valve is usually located close to the original water source. The master valve will prevent wasted water in the event of valve failure or a damaged main line.

Zone  - Also called circuit or stations, a grouping of heads that run at the same time. Zones are necessary to separate different watering requirements and because the water source rarely meets the requirement to operate all of the heads at the same time. The more zones that you have, the better control you will have over your system.