Since the year 2000, people have been able to travel with their pets on overseas trips. Traveling with a pet passport makes crossing the border into different states and countries much easier.
The European Union is currently the only group of countries where actual pet passports exist. A USA pet passport is just the documents you need to get into the USA with your dog.
Every country requires you to have specific documents you need to provide upon entry for your dog. What those documents are depends on the country.
All countries have different requirements for bringing an animal over the border, but most countries have similar rules: you need to prove that your animal is up-to-date on vaccinations and healthy.
It cost us roughly 100 euros and made traveling within the EU much easier and enjoyable with our dog.