What is a 'Market Maker'?

-A 'Market Maker', or MM for short, is a brokerage or bank that is supposed to create an orderly market for a stock. Market makers create a market by maintaining a 'bid' and 'ask' price on each stock they are participating in. The market maker should readily buy or sell the stock when their quoted prices have been met by another party. This is, of course, as long as bid or ask size is sufficient to cover the order. Market makers are critical to creating 'liquidity' and efficient trading for each security they participate.