The pump is connected to the engine, and it pumps fluid (usual oil) in the torque converter. The turbine is connected to the gearbox, and it spins once the fluid from the pump hits it. A nasty transmission filter will induce your gears to grind on each other as well https://brookskxfnt.blognody.com/35904813/new-step-by-step-map-for-filter-gearbox