apply for US passport

Depending on where you are traveling outside the U.S., you will need to decide whether you need passport book or a passport card.
A passport is required for all international air travel.
To enter the United States where land borders or oceans are crossed from Canada, Mexico, the Caribbean and Bermuda, you can use a passport or passport card.
A passport is much simpler and less expensive than a passport, but it cannot be used for international travel by air.