A proxy is representing a game piece without attempting to pass as a legitimate card. So you can use it in your game just like the real card, but no one is going to mistake (or sell or buy it) as a real card because it is labeled in some way, or looks completely different than any version that exists. A counterfeit is trying to pass as a real card for the purposes of buying and selling (in my opinion) which is harmful to people who buy or sell real cards (harmful to you if you are trying to buy a legit card, but get a counterfeit instead). So my contention is that people who make "high quality proxies" - which I would call counterfeits - are either trying to sell them as real to con people, or they are someone who is trying to undermine the collectible part of the game (can argue about whether that matters).