What is Day Trading ?
Buying and selling several times a day to profit.
Buying or selling early in the trading day and exiting on a stop, profit objective or MOC.
Initiating a trade and holding it for a day or two. (Not exactly sure when the exit will occur)
Scalping the market for a few tics. (Multiple contracts or large number of shares)
Market Makers (Matching buyers w/sellers, market makers buy wholesale and sell retail)