Sponsored listings are listings that the seller has agreed to pay eBay a percentage of the sale price in exchange for higher placement in search results. Sponsored listings do not sort the same way that regular listings do because of this.
You may notice that in many sorts, you see the same listing twice -- once as a sponsored listing, and again as a regular ("organic") listing. The organic listing should sort correctly, though if you use "Best Match" you may only see the higher sorted of the two listings.
At various times it was possible to use an ad blocker to remove sponsored listings from search results, leaving only the organic results, but eBay periodically changes the way that sponsored listings are designated, and until the ad blocker rules are updated, the sponsored listings continue to appear.
