If the cell is completely blank (empty), the function returns the boolean value TRUE; otherwise it returns the boolean value FALSE. If the cell contains a space or a nonprinting character, the function returns FALSE, even though the cell appears to be blank.
Examples
If the table cell A1 is empty and cell B2 is equal to 100:
=ISBLANK(A1) returns TRUE.
=ISBLANK(B2) returns FALSE.