The "Tracker" feature on the Chart menu is another way of launching the "Tracker" selection on the charting toolbar.
Upon selecting "Tracker" from the Chart Tools menu, target-style crosshairs will be superimposed on your chart. Use your mouse to position the pointer anywhere on the chart. A data window showing complete numerical market data for the corresponding day also displays.
Click the "Tracker" button on the charting toolbar or uncheck "Tracker" on the Chart menu to remove the crosshair and data window: