OE, shorthand for Original Equipment, parts are the same as what was originally installed on your car and what you'd buy at the dealership parts counter, but with the dealer logos removed by the manufacturer (they will be stamped with the OE's name and logo instead).
OEM, Original Equipment Manufacturer, parts are produced by a manufacturer that supplies OE parts to vehicle manufacturers. Because they are produced side-by-side with OE parts, OEM parts are held to strict quality standards and quality control.
Genuine Or Aftermarket
Genuine parts are sourced directly from the vehicle manufacturer and at a higher cost compared to OE and OEM parts. These are the same parts found on your vehicle, and what you'd buy at your dealership's parts counter.
Aftermarket parts are non-factory parts and accessories that are used to repair or maintain a vehicle. These parts may be produced by a manufacturer that supplies OE parts to a vehicle manufacturer, but not always. Aftermarket parts are not original to the car and are often built with affordability in mind. They may also be the only available option for discontinued Genuine parts.