What does the Union tool do?

The Union tool in ArcGIS Pro is designed to combine multiple input feature layers into a single output feature layer while preserving all the geometry and attributes of the overlapping features. It creates a geometric union of the input features, meaning that it can generate new polygons that reflect both the unique and overlapping areas between the input layers. This is particularly useful in scenarios where you want to analyze how different regions overlap and interact with each other, allowing for comprehensive spatial analysis.

By performing a geometric union, the tool merges attributes from each of the input layers, providing a detailed output that can be extremely valuable for tasks such as land use analysis, environmental studies, and urban planning. Thus, the purpose of the Union tool is fundamentally about the geometric combination of features and maintaining the relationship of their attributes in the result, which is why this option is the correct answer.