      Level II data shows which market makers or ECNs are bidding for oroffering stock, the price, and the number of shares that are being bid foror offered. The more advanced trading platforms also include Time of Sales(TOS), which shows the quantity, price, and time at which trades have takenplace. Some systems reveal which market makers and ECNs have been at theinside bid and ask the most times, second most times, third most times,etc. To fully understand the interaction of these different components, adetailed explanation is in order.