Challenge Cache: A type of cache where you not only have to sign the log, but also complete a challenge. This cache is located at the posted coordinates.
This Challenge: This is the 10 State Challenge. In order to qualify you must find a cache in 10 differenet states.
Check your qualifications here:
My qualifications: 
I have found required number of caches (1) in each of 46 Regions (required number of Regions: 10).