Superfetch is a service in Windows that's designed to speed up app launching by preloading certain apps based on your usage patterns. Tune-Up Blog has a nice explanation of what it does.
However, it should not be maxing out your processor all the time. If it is slowing down your computer, you can try to disable it.
To disable:
Open the Start Menu.
Type "services" and hit Enter
Look for Superfetch in the list and right-click it>Properties
Set the startup type to disabled and click the Stop button to stop the service
Click Ok