A specialist is a member of a stock exchange who works as an auctioneer for a specific stock and/or stocks. It can be an individual, partnership, corporation or group of firms.

The specialist works to maintain a "fair and orderly market" for respective stocks, matching up buyers and sellers by displaying the best "bid" and "ask" prices at its trading post. If buys are not equal to sells, the specialist evens the scale by buying or selling shares, accordingly. However, they cannot make their own transactions until all investor orders have been placed.

Gauging supply and demand, the specialist sets an opening price for the stocks in its domain. If a price has not been set by the time the market opens, the specialist can delay that particular stock's opening.

Specialists make money off the "spread," which is the difference between bid and ask prices on orders.