Hydraulic machinery uses liquid fluid power to do work. A liquid is sent through the machine to hydraulic motors and cylinders where it becomes pressurized due to the presence of a resistance. Valves control the fluid and hoses distribute it. The automotive industry uses production assembly lines with hydraulic systems. The publishing and printing industry use this type of technology. Submarines employ hydraulics to operate ballast tank vents, steering, torpedo tubes and others. In passenger vehicles such as cars and motorcycles, the braking system uses brake fluid to transfer pressure from the contol unit by the passenger to the brake mechanism located near the wheel of a vehicle to stop the car or bike. The force is magnified and can stop a car or bike in the hydraulic system.
Lots of industries use hydraulic power, which is power that is derived from compressing fluids to move things.
Companies drilling into the earth to extract oil, natrual gas, or even water sometimes use hydraulic fracturing, or "fracking", to open up veins within rocks and improve the flow of product. This process has recently become controversial in some parts of the US, because it sometimes works too well, allowing natural gas to find its way to the surface, and into people's homes and water wells.
Hydraulic systems are used on all sorts of excavating machinery, such as the digging arms on most backhoes. A hydraulic drive is powerful and very durable under hard use. Hydraulics also powers jacks and lifts, such as those used in automotive repair shops to raise a car up so it is easy to work underneath.