Private Buyer
  
It's a whispery auction. You don't want anyone to know that you're buying the Matisse. You're a low-key decibillionaire and you want the painting for your entry hall.
Any time we buy something without the explicit support and backing of a government or government entity, we are a “private buyer.” Whether we’re buying a Big Mac or a $20 million Matisse, if we’re doing it on our own, we’re a private buyer. Contrast this with a public buyer, who makes purchases on behalf of a government.
But back to that $20M Matisse for a sec. If we purchase it via a closed auction where no one knows who’s bidding or how much, that’s another type of private buyer: the type who chooses to remain anonymous.