Everyone should know how to shut off the water supply to the home.
The fresh water supply comes from outside the home whether from a city water supply such as mine in Longmont or from a fresh water well if you live in the Colorado country side.
Very near the spot where the water line comes into the home there is a valve that can stop the flow of water into the home. In case of a water damage emergency you will need to use this valve to stop the flow of water. Find the valve and label it so that anyone else can find it as well. Murphy’s law tells us that disaster will strike when you are gone. You will need to be able to tell a neighbor or friend how to locate the valve.
For most homes it will be in a crawl space or the basement. If you have to track it down start by the water heater and identify the cold water supply line. Track that pipe backward to where you see it coming through the foundation wall. That’s where you will find the valve. Very near that same spot will be the pressure regulating valve for the household water supply. Do not mess with the pressure regulator, that’s a job for a professional master plumber.
It could be either a ball valve or a gate valve. It doesn’t matter what style, just identify it and label it so that others can find it easily.