It's very likely that you have seen or interacted with your oil pan at some point. Whether you get your oil changed or you like to do it yourself, it's the spot where the oil is drained from your motor during any oil change. By removing a bolt on the bottom of the oil pan, the oil comes out allowing for additional or new motor oil to be added through the top of the motor in the valve covers. The oil filter is also located right next to the pan and is also changed during maintenance or repairs.