How is the flow of oil in a hydraulic system measured?

The flow of oil in an hydraulic system can be compaired to any water system; in both systems you will find the tank (place where the liquid is store), the conduits or channels through which the liquid will travel (pipes), the pump (to impulse the liquid through long distances or to de a job such as filling a cylinder (piston) or pushing hot or cold water through an air conditioning system in a building, filters (to ensure purity of the liquid), and finally you may have temperature controls. The oil characteristics of a hydraulic system are such that permits the oil to perform amazing work such as keeping a building structure level (this is the case at the outshore airport of Tokyo, which keeps sinking into the see bed and by means of hydraulic systems they turn the support of the structure hydraulic jacks as needed to keep the whole airport level.

The brakes in any car is another example of a hydraulic system where the flow of oil impulse by the brake pedal and or the ABS pump will force the pads of the brakes grab the wheel discs hindering the wheels from turning.

The Power Steering in any car is another example of oil flowing trough pipes to help the driver turn the car around.