For =Fees!$D$9, the word following the =
sign is a name of a worksheet. In this example, the worksheet name is Fees
. !$D$9
is a reference to the cell D9 in worksheet Fees. Using this notation, you can make the value of a cell equal to any other cell in the workbook.
=IF(B16>0.7, Fees!$E$10, 0) is the IF formula. It means that if the value in the cell B16 is greater than 0.7, then set the value of the cell to the E10 cell of the worksheet Fees. If not, set the value of the cell to 0.
Paul