I'm not going to lie, when I first started traveling I thought a Visa and Passport were the same thing and was sitting confused in a conversation with a friend as they discussed the need to get one.
In my mind once I got the passport I was good to go AND the world was now my oyster. Well the world with Wi-Fi and AC, just keeping it real. I did some googlefu and realized rather quickly that they are not one and the same AND ( I keep using that in caps cause I wanna) your passport determines which countries you can visit. Meaning not every country wants you. Well not you but hey...you.
Fortunately I'm an American and the oyster size is still pretty good, almost excellent as determined by Henley & Partners Passport Index. H&P is a ranking of all the passports of the world according to the number of countries their holders can travel to visa-free. Being 4th in this instance, ain't bad at all. Check out the bottom five in comparison.
Below is a visual that shows which countries you can visit with an American passport.
I realized in the middle of this that I didn't define a Visa or Passport. A visa is an endorsement on a passport indicating that the holder is allowed to enter, leave, or stay for a specified period of time in a country. And a passport is an official document issued by a government, certifying the holder's identity and citizenship and entitling them to travel under its protection to and from foreign countries.
In a nutshell you need a passport to leave the US or your home country and a Visa to gain access to "certain" countries.
An advance visa is required for the countries listed below. This means you have to fill out an application and possibly visit that countries Embassy or Consulate to get your Visa.
When I visited China I had to turn over my passport to the passport office here in Georgia for about two weeks or so. Fortunately it was near Atlanta and I didn't have to rely on the good ol US of A's postal service to possibly loose it. And uhmmmm if you didn't know Visa's cost. China was $220, good for 10 years, and my Vietnam one was around $100 and good for 30 days. Blasphemy I tell ya.
The countries listed here allow you to get a visa on arrival or possibly an E-visa. Have funds on hand.
Check your destination’s entry requirements page on the State Department’s website for more details. Visa rules may not apply if you’re entering the country via a cruise ship.
All this to say. Research. And be prepared to pay for more than a flight and a hotel. Or go to the dozens of other countries that don't require a Visa.