The hydraulic system consists of oil, an oil filter, an oil pump, and a valve body (valves and solenoid valves).
The oil pump is powered by the engine. ATF passes through the oil filter and gets distributed along the oil channels.
The oil becomes highly pressurized as it exists in the oil
pump and passes through the line pressure valve before being fed to the
clutch & brake control valve, clutch, and brakes. TCM controls the
hydraulic pressure using solenoid valves and controls clutch and brake
operations.