An OE Car Part refers to any car part fitted to a vehicle from production/factory. It stands for Original Equipment and refers to any part which was originally fitted to the vehicle.
As previously stated, the OE part is the same as ‘factory fitted part’ or ‘genuine part’. It won’t usually be manufactured by the car manufacturer themselves, but by an Original Equipment Manufacturer (OEM) who are a manufacturer of original car parts; Bosch, Mahle, Delphi, TRW, Lucas, Valeo, Hella are all examples of OEM.
Since OE refers to original part it is often considered to be the best in terms of quality as one assumes the OE Part manufacturer must adhere to the original specification of the Vehicle Manufacturer.