What are internally lubricated parts?

What are internally lubricated parts?

ENGINE: Internally Lubricated Parts contained within the Engine, including Pistons, Piston Rings and Pins, Connecting Rods, Connecting Rod Bearings; Crankshaft, Crankshaft Main Bearings, Camshaft, Camshaft Bearings, Cam Followers, Timing Chain, Timing Gears, Rocker Arms, Rocker Shafts, Rocker Bushings, Valves, Valve …