Sotheby's and Christie's are perhaps the best-known auction houses in the world. While they each auction of variety of objects from luxury yachts to premier real estate and collector cars, they also auction art. They may or may not have a single auction dedicated only to art. They may, for example, sell an estate that includes a variety of collectables. They may sell a single art collection in an art auction. These kinds of high-profile auction houses are the most likely venue for the most well-known collector art such as Van Gogh, Renoir or Picasso.
On a local or regional level, auction houses operate similarly to Sotheby's and Christie's but on a much smaller scale with less expensive work. These auction houses tend to be a blend of antique dealers and estate liquidators. They are often hired by families to liquidate the estates of of recently deceased relatives who left valuable collectables. Sometimes individual estates are auctioned. Sometimes, items from multiple estates are conjoined, and auctions are held exclusively for a specific type of antique, collectible or art.
eBay is, of course, the biggest online auction site. And, eBay has demonstrated that big-ticket items can be sold in an online auction format, from diamond rings to jet airplanes. eBay also has individual stores or brands within its online auction format. So, an art dealer or auctioneer can have his own art auction within eBay. Other sites and formats have subsequently added online auction functionality to their operations. Regional auction houses, for example, may have real-time, online bidding.
Many institutions and businesses conduct liquidation auctions from time to time. These auctions don't tend to be highly specialized like most art auctions. They are primarily held to liquidate assets wholesale prices that will attract buyers quickly. These auctions may be for anything from delinquent dues on a storage space to government seizures of assets by law enforcement. The items sold vary widely. From time to time, liquidators will sell a lot consisting almost exclusively of art.