SUM : Adds all the numbers in a range of cells. E,g SUM(3, 2) equals 5, If cells A2:E2 contain 5, 15, 30, 40, and 50: SUM(A2:C2) equals 50, SUM(B2:E2, 15) equals 150.

SUMIF : The SUMIF worksheet function checks for a value within a range and then sums all the corresponding values in another range. SUMIF has three arguments: the range to be checked, the value to check for within the range (the criteria), and the range containing the values to be summed.

=SUMIF(range,criteria,sum_range)