Easy to find out. Go to "my ebay". Click on "advanced" to the right of the search bar, up near the top right. Click on "by bidder", then enter <span style="text-decoration: underline">your</span> bidder name when the box pops up. Make sure you check the box that says " show completed auctions". You will have the winning bidders name (at least their ebay name) and if you click on that, then if you still want more information, look at the history of that bidder name and you will most likely know who it was. But then, you will sometimes find people like me that use different names as a buyer than they use as a seller, so the name takes you to a dead end. Then you may (I'm only saying "may"
find out someones buying name if you are a seller and they buy one of your items. If you run across someone that has five or six different buyer and seller i.d.'s, this all goes out the window. Good luck.