What functionality does the 'Data Validation' feature provide in Excel?

The 'Data Validation' feature in Excel is designed to set rules for what data can be entered into a cell or a range of cells, which helps ensure data integrity. By applying data validation, users can limit the types of values that can be entered, such as restricting entries to numbers within a certain range, requiring a specific format (like dates or text length), or creating a drop-down list of acceptable options. This functionality is essential for maintaining accurate and reliable data in spreadsheets, particularly when working with data inputs from multiple users or when the data will be used for analysis.

In contrast, the other options do not capture the purpose of the 'Data Validation' feature. Changing cell colors is a formatting action, automatic chart generation pertains to visual data presentation, and merging cells involves altering the structure of the worksheet layout rather than validating data input. Thus, the correct answer highlights the critical role that 'Data Validation' plays in maintaining consistent and reliable data.