A Genuine part is a part that is originally put in your vehicle when it was new and has the car manufacturer's logo on it. This does not mean the product is actually made by the car manufacturer; it is often made by a different company but the car manufacturer's logo is added.
An Original Equipment Manufacturer part is a part built by the same company that built the original product for the car maker. It is the exact same part that is in your car, except it does not have the car maker's logo. These parts are the same as the Genuine part but cheaper as you are not paying for the privilege of having the car maker's logo.
Replacement parts and accessories. Replacement parts are automotive parts built or remanufactured to replace OE parts as they become worn or damaged. Accessories are parts made for comfort, convenience, performance, safety, or customization, and are designed for add-on after the original sale of the motor vehicle.