Final answer:
The NASDAQ is the most significant dealer market in the United States, where trades are made via market makers, while the NYSE is the foremost auction market, with transactions being made through the highest bid matching the lowest ask.
Step-by-step explanation:
The NASDAQ is the most important dealer market in the United States, and the New York Stock Exchange (NYSE) is the most important auction market. The NASDAQ operates as a dealer market where trading is between buyers and sellers through a market maker rather than directly with each other.
On the other hand, the NYSE operates as an auction market where buyers and sellers conduct transactions through an open outcry system, or more commonly today, an electronic system where the highest bidding price will be matched with the lowest asking price.