Keyed different means each lock has its own key. Each individual lock will require a specific and unique key in order to access it.
Benefits:
Keyed different locks are the most secure option available. You'll be able to rest easy knowing that by losing a single key, you won't lose control over all of your other locks.
Negatives:
While keyed different locks are more secure, they are also a heavier burden. You'll have to handle multiple keys depending on how many locks you have on your property. This means that you'll need to have a large keyring with you at all times.