Be World Wise, Know Before You Go
Most passports are the same, they state your name, a picture of you, your birthdate, your signature, and the expiration date. For most countries a passport is required, that way when you apply to go to another country they can verify who you are and where you come from. But before you go you should research their laws. Most countries are very different from the United States. For example, in some countries it is illegal to pull over when a police car is coming because it is a sign of guilt. Another one: in Singapore there is a list of forbidden items that you can face huge fees for if you bring those items into their country. This lists includes items such as chewing gum, controlled drugs and psychotropic substances, endangered species of wildlife and their by-products, firecrackers, video tapes/discs and software. You can find information on any country at this link.
It is best that if you are going to travel go in a group (cruise, tour,etc.). There will already be locals or guides that know the customs of that country; they will have guards and other forms of protection for you. For example, in Rio de Janeiro after dark the gangs come out with machine guns and will kidnap U.S. citizens for money, so all the tour guides carry guns with them.
In a lot of countries the U.S. has set up a resource center for American citizens, they are called the U.S. Embassies. The Embassy provides information, help ( legal or medical), basically anything an American citizen could need while in a foreign country.
Visas are another form of passport but the difference is that a visa specifies the reason that person is in that country and a visa has a time frame. But you still need your passport when going into a country with a visa. Visas are usually used for students who plan to attend a school in a different country or someone who got a job in a different country. For certain countries you need a visa to get into their country no matter the reason you are there for (Brazil, Peru).
When you apply to go to another country there is always a waiting period and a fee. The fee varies depending on the country.