If you have a building with a basement you will find many items in it that help your house function .  It often has many devices that should be understood like the Furnace and Water Heater, also the Main Water Shutoff and drain cleanouts ,  Outside Faucet Shutoffs and little known items like the Pressure Regulator ,  the Doorbell Transformer ,  telephone wires and connection blocks  and Who Knows What else .
    Often these items are hidden in the Floor Joists or in the walls if they have been finished or in a utillity room or closit .
You Should already know how to turn off your water in case a pipe bursts or you need to do a repair in your houses plumping . but if you are not sure where it is or where to find it and you have an emegency the city  ( or fire department) can shut off your homes water at the street . The Shutoff will be very close to where the water comes into the house , and the drain cleanout will be near where the sewer leaves the house