How does a spool valve work and where are they used?

Spool valves are widely used in many industries, spool valves are used in hydraulics, in which the oil is the energy source and they are also used in pneumatics where the air is the energy source and spool valve does the flow direction of the energy source and these valves does this by combining or switching the paths through which the oil or air can travel. A spool valve is a cylinder inside a sealed outer case and there are several chambers drilled through the case from one side to the other and these are called ports. The major function of the spool is to move within the sealed case and does the opening and closing of these ports depending on the position of the spool. Spool can be moved in many different ways it can be done manually. The energy sources and components are connected to a spool valve by ports and they are the chambers drilled through the outer casing of the valve. Spool valves can be operated in many ways like by using a button, lever, or by a solenoid. Mostly spool valves are referred by 3/2 or 5/3 etc. In which the first number represents the number of ports and the second one represents the spool position. Spool valves are of a wide variety and many types of configurations, some have more ports and are able to control multiple items of equipment at once. The blocking part of the spool is known as lands, and they are raised above the spool core, and if these are made different in configurations they can change the way the port pathways interconnect.