1. Academic Students (F visa)
In the United States, students must be admitted to full-time classes of 18 hours or more per week in an academic program in order to study with an F-1 visa. To obtain a F-1 visa, it is also necessary to get an I-20 document issued and managed by SEVIS (Student and Exchange Visitor Information System) based on admission to a U.S. academic program. The most important requirement for getting a student visa is to have adequate and proven financial support to enable you to live and study in the United States. If your family, employer or sponsor, in the form of an institution located in your home country, is financially supportive, your visa issuance is likely to be successful. It is also important that there is an intention to return to Korea after a lawful stay.
2. Exchange students, scholars, professors, or researchers (J visa)
To obtain a J visa, you must first have a secure residence in Korea, a common element of nonimmigrant visas. Like a F-1 student visa, there should be a clear assertation that you will return to Korea after the legal stay with the nonimmigrant visa. This J visa require a sponsoring program approved by the US Department of State. You need to get an official letter that approves J-1 visa from the US Department of Statement (i.e., DS-2019), and it is usually issued by a DSO (Designated School Official) from the school or research institute, such as I-20 on a student visa.
J visas differ significantly from other non-immigrant visas, so you should be careful when you first receive them. Although not all J visas, most J visa holders have a requirement that they must return to their home country for a period of two years after the legally permitted period of stay of the program has expired. Otherwise, it is not possible to apply for permanent residency or change your status in the United States.
3. Nonacademic or Vocational Studies (M visa)
M visa is a visa only for job-related technical education, not academic or general academic education, and is issued when you are trained at vocational training schools such as nail beauty, skin care, specialty cooking school and golf school. There are a variety of community colleges and other two-year colleges that offer a two-year technical degree, but language schools that offer English language programs is not applicable for M visas.
M-Visa holders cannot change their student status (F-1). To study as a student, you must go back to Korea and obtain an F-1 visa at the US Embassy. You may change your status to H-1B (short-term employment visa) while you are on your M visa, but the most important thing for you to get an approval from the USCIS is not to work with what you learned from your M-1 status. That is, when you change to an H-1 status, you need to prove that the skills you need to work in an H-1B status are those you have already acquired before studying with an M-1 status.