What do you use to group columns or rows in Excel?

The Outline feature in Excel is specifically designed for grouping rows or columns to help organize data effectively. When you use this feature, you can collapse or expand groups to make your spreadsheet more manageable, allowing for better presentation and analysis of large sets of data. This is particularly useful for summarizing and structuring information in a way that makes it easier to navigate, as it helps in hiding or displaying details as needed.

In contrast, the other options serve different functions. Data Validation is used to control the type of data entered into a cell, ensuring it meets specific criteria. The Merge and Center option combines multiple cells into one and centers the content, but it does not offer any grouping capabilities. Cell Styles allow users to format cells for visual appeal but do not provide any functionality for grouping data. Therefore, the Outline feature is the appropriate choice for grouping rows or columns in Excel.