DOM (the book) - list of all BID and ASK limit orders with size waiting for execution. A lot of day traders using this tool for market analysis. If on the DOM exists really big sell offer, then the bid price would fall. If on the DOM exists really big buy offer, then the ask price would jump. Divergence between BID and ASK makes price movements. OTC scalpers using this tool, can open quickly (in a second) position and close with couple points earnings.