Original manufacturer parts, or OEM parts, are car parts that are made by the auto company that also made your car. When you buy a new car, it comes with all OEM parts, but there are plenty of third-party companies making what are called aftermarket parts as well.
Aftermarket parts have their advantages, including a price tag that's usually a bit lower than OEM parts. They're also more widely available at independent repair shops, and if you buy the right kind you can get high quality aftermarket parts.
But these benefits don't outweigh the disadvantages. The quality of OEM parts is much more reliable and consistent, and it can be difficult to find aftermarket parts that match the quality of OEM parts. Plus, there are so many companies selling aftermarket parts that it can be a stressful buying experience even for longtime car owners.
If you typically service at a dealership, OEM parts are readily available, and while aftermarket parts are rarely warrantied and require extra research to find out for sure, OEM parts almost always are. Plus, experts agree that OEM parts are by far the best choice for collision repairs.
Between the free warranty, which more than makes up for the difference in cost, and the increased reliability of OEM parts, it's clear aftermarket parts are a riskier choice and can be more expensive in the long run even with lower initial costs, so seriously consider picking OEM parts!