Visa is an unconfirmed permission approved by the Govt. of a country to enter a person who is a non citizen and allow him/ her to stay temporarily in a given period of time within the country.
Visas generally comprise the period of stay of a person, date and duration of stay, type of visa etc. Visas are required when a person wants to visit a country 
with a reason whether it’s for employment, for educational purpose, some job training and so on. For all reasons a person need to request for visa to enter in a foreign country. It is completely the subject to permission given by the department of immigration and can be cancelled at any point of time if documents are not appropriate.
Visa stamp is usually done on the passport of the applicant. You need to show the visa at the time you enter in a visiting country.
There are several companies available for all kind of travel related works and visa stamping. You can take their help in completing your travel plan as these companies are authorized and registered by the government authorities. There are several types of visa for individual requirement for eg., tourist visa, employment visa, education visa and many others.
Source:http://www.talentattestation.com/news-updates/hajj-and-how-it-affects-your-visa.html