A leak in the supply pipe.
Air in the water lines to the upstairs. Not enough water pressure.
check for leaks
Lots of stuf can cause it including sediment or a blocked supply line
I would purchase a Watt water pressure guage from your local home improvement or hardware store and check your water pressure at your faucet. If water pressure is greater than 40-45psi your regulator needs to be turned down where the water comes into the house.
Stopped at all faucets? Didn't pay the water bill. If in cold climate, the line from the outside to probably the water heater has probably frozen.
Possibly a pressure reducing valve installed after piping for first faucet, which would cause situation describing.
With no air in the system anywhere, there would be nothing to hold pressure, so the slightest leak would cause the system to go to zero.
Voltage pushes current through a circuit. A good example of how this works would be water pressure and flow. your faucets at home as long as they are closed have water pressure on them but no flow. You open a faucett and the water starts flowing pushed by the pressure. The voltage is represented by the water pressure and the Current (amps) is represented by the water flow.
Do all the faucets do this or just one. if its just one faucet its a problem with this fauset. If its all the faucets in the home its a problem with the main water line coming into your home.
There is no water, or water pressure reaching the faucet. This could be that your local water service was shut off; either from no payment, or to fix water lines - to, failure of your well (if you are on a well service) or a rupture of your main supply pipe (of such a severalty that you are getting no pressure).
Most of the newer kitchen faucets have "flow restrictors" to limit water use.