What is the primary purpose of a geoprocessing model in ArcGIS?

The primary purpose of a geoprocessing model in ArcGIS is to automate repetitive tasks. Geoprocessing models allow users to string together multiple geoprocessing tools into a sequence, enabling the execution of complex workflows with just a few clicks. By automating these tasks, users can save time, reduce the potential for errors, and enhance productivity, especially when dealing with large datasets or when a process needs to be repeated multiple times.

In a geoprocessing model, users can define inputs, specify processing steps, and manage outputs efficiently. This functionality is particularly beneficial in scenarios where the same analysis is required across different datasets or time periods. By creating a model, users can ensure consistent results and easier adjustments when needed.

The other options presented, while related to the GIS environment, serve different purposes. Visualizing spatial data focuses on representing data effectively through maps, creating map layouts involves designing finished cartographic products for presentation, and developing web applications pertains to creating interactive content for users to engage with geographic information online. These tasks do not encompass the primary function of model automation, which is the essence of what geoprocessing models contribute to ArcGIS workflows.