Do you know where your shutoff valve is?
In case of a plumbing emergency, it is always a good idea to educate yourself on how (and where) to turn off your main water supply - as well as the isolation valves on your various plumbing fixtures. A ruptured line, burst pipe, or sewage backup can wreak havoc on your home and potentially cost you thousands in water damage and water bills.
In severe cold weather, the water in your pipes can freeze. When water freezes, it expands and can burst the pipe, not matter how thick or strong it may be. If it's too late and the pipe has already burst, turn off your main water valve as fast as you can to prevent further damages.
Being able to contain the situation as soon as possible will greatly help with damage control and allow a wider window of time for help to arrive (if the situation calls for it). Everyone in your home should know exactly where the water shutoff valve is located and how to turn it off.
Additionally, if you are going to be away from your home for an extended period of time, it is highly recommended that you turn off the main water valve.
Where is the main water shutoff valve located?
This is the million-dollar question. Your main water shutoff valve could be located in several different areas. If you have a home with a basement and crawlspace, it is probably located on an interior wall near the front of the house, where the water comes in from the water meter. In this case, it is most likely hiding in plain sight. If your home was built on a slab, the valve might be located near the hot water heater or inside your garage.