A Market Maker ... on Level 2 - :-D
A market maker is a company, or an individual, that quotes both a buy and a sell price in a financial instrument or commodity held in inventory, hoping to make a profit on the bid-offer spread, or turn. From a market microstructure theory standpoint, market makers are net sellers of an option to be adversely selected at a premium proportional to the trading range at which they are willing to provide liquidity... etc...