How to travel internationally?

Like where do you go to get your passport and Visa? And do you always need a Passport and Visa? Or just when going into further away or possibly unfriendly countries?

How easy or hard is it?

I've seen a Customs show in Europe, seemingly showing them reject a lot of people from international, but of course they're just showing the most exciting case they can find and the people that pass by probably aren't exciting.