Instinctively, dogs will not soil the area where they sleep. Therefore, a crate can offer your dog a place to rest without the risk of going potty in his safety zone. Ideally, this will teach your dog to hold it and wait for you to let him out. Of course, if left alone for an unreasonable amount of time (or if ill) the dog may go potty in the crate. Don't punish the dog in these instances. Simply clean the crate and eliminate the smell so the dog can return to his comfortable spot again.
Crate training also keeps your dog from testing his limits and getting into things while you aren't home. He can't give in to the urge to destroy things to get attention if he is confined to his own personal space and doesn't have access to your things.
