In this article I will give an overview of options available to these 2 categories of people. Keep in mind that these options are by no means exhaustive. Each individual case is unique and therefore a consultation with an immigration attorney is the only sure way of receiving comprehensive legal advice.
All visas serve as U.S. entry documents.
Visas can be designated as either immigrant or nonimmigrant. Immigrant visas are issued to those who will live in the U.S. permanently and get green cards. Everyone else gets nonimmigrant visas. In order to enter the U.S., you must have a visa. Therefore, when you are granted the right to a green card, you are issued an immigrant visa.