Total all the values in a column
B3:B6 is the information, called the argument, that tells the SUM function what to add.
By using a cell reference (B3:B6) instead of the values in those cells, Excel can automatically update results if values change later on.
The colon (:) in B3:B6 indicates a cell range in column B, rows 3 through 6. The parentheses are required to separate the argument from the function.