Syringes are used to collect blood for laboratory testing. When the plunger of the syringe is removed, the pressure of the liquid (blood) compels the liquid to travel into the syringe. When air is pulled out of a drinking straw, the air pressure within lowers, and the outside atmospheric pressure forces the liquid to enter the straw. This is how balloons are filled with water or helium. Pressure can also be used as a force. For example, in order for ink to flow through pen tips, there needs to be enough pressure behind the ink so that it pushes its way through the plastic barrel or tube. High pressure can also be used as a heat source. High-pressure steam is used in industrial processes where the heat from the steam is needed to do work such as melt metal. The pressure of the steam is so high because it's coming out of a boiler that only uses water to make the steam. The heat from the steam is then used to heat other things around it including tools used by workers. Low pressure is when there is not enough pressure pushing something else away from it to keep it together. If a balloon is at low pressure, anything that releases any amount of air will cause it to collapse. This is why balloons need to be filled with enough air to keep them afloat without being too full - otherwise they would have collapsed by now. As you can see, pressure has many different uses.