Passport card
 

So what is the difference in a Passport and a passport card. I did notice the card is less expensive, only $15 for minors as oppose to the $80 Passport for minors. So this is why I ask this question.

It looks like the Passport Card is ONLY good for entering / exiting the US from Canada, Mexico, the Caribbean, and Bermuda. It CANNOT be used for International travel by air, so most people don't think this is a good idea. In other words, if you go to Europe, or for that matter, Mexico by air, then you must have a passport book in order to enter / exit the US.

Here is the link to the information directly from the Unites States State Department.

In common terms, a passport card is really just 'good I.D.' and unless you live near the Canadian or Mexican borders and cross them routinely it isn't really that useful on a routine basis. However, as I said it 'is' good ID and also a good choice for carrying ashore in the various ports in lieu of carting a book passport around. Thus I ordered the cards with my current passport renewal. When we go ashore on cruises we will carry our passport cards as photo ID. Less chance of losing a driver's license that way.