just like watering the garden. Putting the bozzle in the "jet" position makes the water flow slower at any of the squeezed positions.
The water pressure inside the pipes (inside the house) is fixed, however, by squeezing the end, the total flux of water is reduced, therefore the pressure drop in side the tube or hose is reduced. The difference betweem the pressure inside the house pipes and the atmospheric pressure is then focused at the place where water is released. So squeezing leads to faster flow.