Water meters and water service lines cannot provide enough water to water an entire yard at once, so the system is typically broken up into several individual zones or stations. Flower beds verses grass, sunny areas verses shady areas, etc. Valves are typically installed near the area they water. There are two basic types of valves being used today. Manual valves, that require a person to turn them on and off, and automatic or electric valves, that are operated by the electric controller.
Manual valves require very little discussion.
Systems with manual valves are seldom installed today. Existing manual valve systems can be easily upgraded to automatic control for reduced hassle and greater efficiency by a professional contractor. Automatic valves are a bit more involved, but you would be amazed at the simplicity of the technology that operates these devices. Most modern systems installed today rely on automatic electric valves. Most automatic valves operate on 24-volt electricity.