Ebay is a good contrast here, as while it has the same general search-for-a-thing idea, it makes it very clear that you're buying this one specific item from this one specific merchant.
I could buy the same goods on Amazon but have none of the traceability or protections.
If I'm buying a second hand item like an old video game or something I always use Ebay since I can see what the product actually looks like and can make my own judgement on condition based on the photos. Something you can't really do on Amazon.