Every country has its own visa requirements. Visiting another country normally means that you will need a visa. On the other hand, there are a lot of exceptions when it comes to your country of citizenship and the country you are visiting.
People from neighboring countries may not require visa, and sometimes people holding passports from few countries might not require visa as well. For some countries, a person will have to get visa from the embassy, while other countries, a person can get a visa from the airport after landing to the country you are going to.
All in all, it is important to understand the rules, and get proper documentation before visiting any country.