The Parvo virus is a gastro-enteritis virus affecting dogs.
These sites give more information.
http://www.napoleon.org.uk/health/parvo.htmhttp://www.inkabijou.co.uk/parvo.htm
From you nickname I guess you may have a puppy! If you have any concerns about the virus or are worried he/she may have this, take him/her to the vet promptly, as only they can diagnose and treat this illness properly.