Basically it means you are getting a top of the line puppy!
A champion sire or dam, means that one of the parents or both has repeatably won FCI organized conformation shows and must therefore be of excellent appearance and conformation.
Literally this means, by the rules of the FCI, that the dog has won the necessary number of local or international dog shows to have been able to earn a Champion or International Champion title. For detailed information of the requirements, visit the official FCI website.