VISA is an approval that grants one the permission to travel to other countries and also defines his/her status in that country. There are 2 main kinds of Visas, Immigrant Visa and Non-Immigrant Visa.
People who are planning to migrate or settle down permanently in a particular country of which they are not currently citizens require the Immigrant Visa. The Non-Immigrant Visa is a temporary Visa, which does not permit one to become a citizen of that country, but he/she can visit that country for a specified time. A student is required to apply for a Non-Immigrant Visa.

Student Visas are issued for the period it takes the visitor to complete his/her course of study, program or work assignment.