Newb needs help identifying motor area with a possible leak?

[codrMechanix]

I'm in the market for a 4runner and was looking at a 2018 Limited when I noticed an area on the back passenger side of the motor that had some type of oil/dirt covering it. I didn't take a picture unfortunately, but I've included a photo (highlighting the area in question in blue) of a 2019 limited that was not dirty.

Would anyone be able to tell me what might be leaking/dripping in this area of the motor???

Thanks in advance!