Severity. The difference is in the seriousness and severity. People woth gluten sensitivity can somewhat (although they should not) get away with eating gluten, while those with sprue are totally asking for much trouble if they touch gluten.
Yes. Celiac sprue (celiac disease) is gluten allergy, a strong allergic reaction to gluten (a protein in grains such as wheat, barley, rye, etc...). Gluten intolerance is not an allergic reaction, but does lead to tummy symptoms such as gassiness, bloating, loose stools, etc... Gluten intolerance does not damage the intestine. Both celiac sprue and gluten intolerance are types of gluten sensitivity.