It is just the cookies you are dragging around the internet. You have obviously been on CHevy related sites or car sites and Chevy is trying to get you!!! Heck, I just spent the last week in Costa Rica and my Chevy ad is in Spanish!!!!
I never see ads on TF. I guess my ad blocker is working pretty well. I do see ads on Facebook that I can tell are related to various searches, cookies, etc.