The primary purpose of sProps is to allow you to breakdown Page Views, Visits and Unique Visitors into meaningful buckets.
An important thing to know about sProps is that they are not persistent. This means that they do not retain their value from one page to the next,
Another important thing to know about sProps is that they are used for Pathing. Pathing is the ability to view the order in which values are passed to a particular SiteCatalyst sProp for a specific Visit.