SUMIFS is a powerful Excel function that allows you to sum values based on multiple criteria applied across different ranges. It's particularly useful when you need to add specific values that meet several conditions.

Here's a breakdown of how SUMIFS works:

Syntax:

```excel
=SUMIFS(sum_range, criteria_range1, criteria1, [criteria_range2, criteria2], ...)
```

Arguments:

* sum_range: This is the range of cells containing the values you want to add. These values must be numbers or formulas that return numbers.
* criteria_range1: This is the first range of cells you want to apply a criterion to. It should correspond to the same number of rows and columns as the sum_range.
* criteria1: This is the condition you want to apply to the first criteria_range. It can be a number, text, expression, a cell reference, or a wildcard character (* or ?).
* [criteria_range2, criteria2], ...: You can add up to 127 additional criteria pairs. Each pair represents another range and its corresponding condition for filtering the sum.

Example:

Imagine you have a data table with product codes, colors, and sales figures. You want to calculate the total sales for red shirts (Size M or L). Here's how you would use SUMIFS:

```excel
=SUMIFS(C2:C10, B2:B10, "Red", A2:A10, {"M","L"}) // Assuming data starts from row 2
```

- C2:C10: This is the sum_range containing the sales figures (column C).
- B2:B10: This is the first criteria_range containing the product colors (column B).
- "Red": This is the first criteria (text) specifying the color to filter.
- A2:A10: This is the second criteria_range containing the product sizes (column A).
- {"M","L"}: This is the second criteria (an array of text) specifying the desired sizes (M or L).

Using SUMIFS effectively:

* Multiple Criteria: SUMIFS shines when you need to consider multiple conditions simultaneously.
* Logical Operators (Excel 365 and later): If you have Excel 365 or later, you can use the IFS function for more complex logic within your criteria.
* Error Handling: Consider using the IFERROR function to handle potential errors like #DIV/0 or #NA that might arise during calculations.
* Clarity: Descriptive cell names can improve the readability of your formulas.

By mastering SUMIFS, you can perform complex conditional summations in Excel, saving you time and effort when dealing with large datasets.