Visitor visa is synonymous with tourist visa. When trying to figure out what application process you have to follow, the embassy website will often have visitor visas under tourist visa. They both relate to the same thing. A tourist/visitor visa means you will be staying in the country for a relatively short period of time and you will not be there for business, work or study.
Some nations require that you got through a formal application process to gain a visa. These counties have different regulations. Some will require medical clearance, which may include vaccinations and HIV/ AIDS tests. Other countries will require a criminal background check. Each country is different, so make sure to check the host country's embassy website before travel.
Several counties have treaties with the United States to encourage foreign relations and tourism. This means that several counties will waive a visitor visa for those coming into the country for a short period of time. Most of the time, each person will be granted 90 days upon entry. Longer stays will require you to fill out a visitor/tourist visa application.
The United States has treaties with several nations that make it so you do not need to apply for a visitor visa when entering the United States on vacation. If you are coming from any of the applicable nations, then a visa will be issued upon entering the nation, and it is valid for 90 days.
There are several agencies that work with people in filling out the visitor visa application. Sometimes this will be recommended by the host nation. In working with outside companies, they will help you complete the process with no/minimal errors before submitting the completed application to the embassy.
