drive shaft oil seal
This is why older cars with very low miles are not always a great deal if they just haven't been driven all that much - 2018 is not old, but plenty of folks buy collector cars from 30 years ago or so and find the car isn't exactly the same as having bought it new or low mileage 30 years prior. Stuff dry rots, or just goes bad for a variety of reasons. Fluids varnish up, or humidity issues on motors not started in some time, lack of proper warm up, etc.. can contribute to all manner of problems depending upon how the vehicle is stored, where it is stored, etc..
If the seal needs to be replaced, it is at least relatively easy to do so versus the front seal, or a rear main seal, head gasket, etc..
Good luck






