OEM parts are Original Equipment Manufacturer parts. This means it is a car part made by or specifically for the car manufacturer.
With OEM, you have a greater assurance of quality as the part will work exactly like the part you are replacing and works the way the manufacturer intended it to work.
Using low quality parts often results in poor performance and decreased fuel efficiency.
It is easier to choose a part. If you go to car parts shop, there is usually limited OEM parts Unlike other parts which has many different brands to choose from and buyers are never quite sure which brand to select.
OEM parts have longer warranties, usually a year, which means parts can be replaced easily.
Not all parts are created equal but all OEM parts are. OEM gives you peace of mind.