Nonimmigrant visas are for temporary visits to the USA for purposes such as being a tourist, to work, to invest or to study.

Immigrant visas are permanent stays in the USA, i.e., the Green Card (Legal Permanent Residency) for people who will be immigrating to the USA.

To visit the USA, citizens of most countries are required to obtain a visa from a US Consulate/US Embassy outside the USA. However, there are exemptions. Citizens of Visa Waiver Program countries are not required to obtain a US Visa to visit the US. In most cases, they only need to obtain an electronic authorization prior to seeking admission into the USA using the ESTA system. There are 38 countries in the Visa Waiver Program:

ESTA is an online portal used to register your eligibility to enter the USA under the Visa Waiver Program. If you are a citizen of a Visa Waiver country, you must register with ESTA prior to coming to the USA. ESTA stands for Electronic System for Travel Authorization. Your ESTA eligibility is valid for 2 years, after that time, you must register with ESTA again to continue visiting the USA under the Visa Waiver Program.

Generally, Canadians are not required to obtain a visa to visit the USA. Furthermore, the process to obtain a work permit for the US is easier as compared to people from other countries. Canadians may often enter the USA using only their NEXUS card or their Enhanced Driver’s License.

There are two types of immigrant visas: a 2-year Conditional Green Card (also known as Conditional Legal Permanent Residency) that requires that some requirement be met before the Green Card can be renewed, and the Permanent Green Card (also known as Legal Permanent Residency).  However, there are 109 different ways of qualifying for a Green Card. Most individuals obtain their Green Card via a family member or an employer in the USA. Other individuals obtain their Green Card via the refugee status, the asylum status or other humanitarian processes. Meanwhile others are eligible to apply for themselves without the need for family or an employer.

There are 83 types of Non-Immigrant Visas.  Here is a complete list:

1. A1 Visa for heads of state, government ministers, ambassadors, career diplomats or consular officers and their immediate family;
2. A2 Visa for ministers of state, other government officials or employees and their immediate family;
3. A3 Visa for the attendants, servants or personal employees of A1 or A2 visa holders and their immediate family;
4. B1 Visa for temporary visitors for business, domestic employees, academics, researchers and students;
5. B2 Visa for temporary visitors for pleasure including vacation, tourism and medical treatment;
6. B1/B2 Visa for temporary visitors for business and for pleasure;
7. C1 Visa for persons in transit desiring to enter the US as a passenger to join a vessel or aircraft;
8. C2 Visa for persons in transit to United Nations Headquarters;
9. C3 Visa for foreign government officials and their immediate family, as well as attendants, servants or personal employees in transit;
10. D Visa for crewmembers of aircraft, boats, ships and vessels;
11. E1 Visa for treaty traders (those in the import/export business) and their immediate family (also known as the Import/Export Visa);
12. E2 Visa also known as an Investor Visa for investors and their immediate family (an Investor Visa);
13. E3 Visa is a work visa for citizens of Australia working in a specialty occupation;
14. E3D Visa for the spouses and children of E3 Visa holders;
15. E3R Visa is work visa for returning E3 Visa holders, those who already have the E3 and are applying to renew the E3 status/visa;
16. F1 Visa is a student visa for students in academic or language schools;
17. F2 Visa for the spouses and children of F1 Visa Holders;
18. F3 Visa is a student visa for Canadian or Mexican commuter students of an academic or language school;
19. G1 Visa for principal representatives, of recognized foreign governments, to an international organization, staff and their immediate family;
20. G2 Visa for other representatives, of recognized foreign governments, to an international organization and their immediate family;
21. G3 Visa for representatives of non-recognized foreign governments to international organizations and their immediate family;
22. G4 Visa for international organization officers or employees and their immediate family;
23. G5 Visa for the attendants, servants or personal employees of G1, G2, G3 and G4 Visa Holders and their immediate family;
24. GB Status* is an immigration status for temporary business visitors from Guam under the Visa Waiver Program;
25. GT Status* is an immigration status for temporary pleasure visitors from Guam under the Visa Waiver Program, includes vacation, tourism and medical treatment;
26. H1B Visa is a work visa for persons working in a specialty occupation;
27. H1B1 Visa is a work visa for citizens of Chile or Singapore working in a specialty occupation;
28. H2A Visa is a work visa for temporary workers performing agricultural type work when a shortage of agricultural workers exists in the USA;
29. H2B Visa is a work visa for temporary workers performing non-agricultural type work when a shortage of such workers exists in the USA;
30. H3 Visa for temporary workers or trainees and their immediate family (excludes graduate programs and medical training);
31. H4 Visa for the spouses and children of H1, H2, and H3 Visa Holders;
32. I Visa is the Reporter visa/Media visa for representatives of foreign media outlets and their immediate family;
33. J1 Visa for exchange visitors;
34. J2 Visa for the spouse and children of J1 visa holders;
35. K1 Visa is a fiance visa for the fiance of US citizen;
36. K2 Visa for children of K1 Visa Holders;
37. K3 Visa is spouse visa for the spouse of US citizen awaiting availability of immigrant visa (a Green Card);
38. K4 Visa is for the children of K3 Visa Holders;
39. L1 Visa is a work visa or an investor visa for intra-company transferees (includes both L1A for executives and managers and L1B for specialized workers);
40. L2 Visa for spouses and children of L1A and L1B Visa Holders;
41. M1 Visa is a student visa for vocational students or for students of another type of nonacademic program;
42. M2 Visa for spouses and children of M1 Visa Holders;
43. M3 Visa is a student visa for border commuter students, from Mexico or Canada, in a vocational or non-academic program;
44. N8 Visa for the parents of children holding the SK3 special immigrant status;
45. N9 Visa for the children of N8 status holders or of SK1, SK2 or SK4 special immigrants status holders;
46. NATO 1 Visa for high ranking representatives from NATO member states or staff and their immediate family;
47. NATO 2 Visa for the members of the NATO military forces and their immediate family;
48. NATO 3 Visa for the official clerical staff of NATO 1 and NATO 2 visa holders and their immediate family;
49. NATO 4 Visa for NATO officials, other than officials in the NATO 1 category, and their immediate family;
50. NATO 5 Visa for the experts, other than officials in the NATO 4 category, employed for NATO missions and their immediate family;
51. NATO 6 Visa for the members of the NATO civilian component and their immediate family;
52. NATO 7 Visa for the attendants, servants or personal employees of NATO 1, NATO 2, NATO 3, NATO 4, NATO 5 and NATO 6 Visa Holders and their immediate family;
53. O1 Visa for persons with extraordinary abilities in the arts, education, sciences, business or athletics;
54. O2 Visa for the support personnel of O1 Visa Holders;
55. O3 Visa for the spouses and children of O1 Visa Holders or O2 Visa holders;
56. P1 Visa for athletes or the members of an entertainment group with international recognition;
57. P2 Visa for the artists or entertainers of a reciprocal exchange program;
58. P3 Visa for the artists or the entertainers of a culturally unique program;
59. P4 Visa for the spouses or children of P1 Visa Holders, P2 Visa Holders or P3 Visa Holders;
60. Q1 Visa is a work visa for the trainees and employees of an international cultural exchange program;
61. R1 Visa is a religious visa for ministers and persons in a religious vocation or occupation;
62. R2 Visa for the spouses and children of R1 Visa Holders;
63. S5 Visa for informants cooperating with law enforcement on the prosecution of criminal activity;
64. S6 Visa for informants cooperating with law enforcement on the prevention or prosecution of terroristic activity;
65. S7 Visa for spouses, children and parents of S5 Visa Holders or S6 Visa Holders;
66. SIJS Status* also known as the Special Immigrant Juvenile Status. This applies to qualifying children in the USA who have been declared dependents of a juvenile court and who risk being harmed if removed from the USA;
67. TN Visa is a work visa for NAFTA professionals (citizens of Mexico and Canada working in a professional level jobs);
68. TD Visa for the spouses and children of TN Visa Holders;
69. T1 Visa for the victims of severe forms of human trafficking;
70. T2 Visa for the spouses of T1 Visa Holders;
71. T3 Visa for the children of T1 Visa Holders;
72. T4 Visa for the parents of T1 Visa Holder, when the T1 Visa Holder is under 21 years of age;
73. T5 Visa for the brothers/sisters of a T1 Visa Holder, when the T1 Visa Holder is under 21 years of age, and the brothers/sisters are unmarried and under 18 years of age;
74. U1 Visa for the victims of criminal activity;
75. U2 Visa for the spouses of U1 Visa Holders;
76. U3 Visa for the children of U1 Visa Holders;
77. U4 Visa for the parents of a U1 Visa Holder, when the U1 Visa holder is under 21 years of age;
78. U5 Visa for the brothers/sisters of a U1 Visa Holder, when the U1 Visa Holder is under 21 years of age, and the brothers/sisters are unmarried and under 18 years of age;
79. V1 Visa for the spouses of lawful permanent residents (Green Card holders) awaiting availability of immigrant visas (Green Cards);
80. V2 Visa for the children of lawful permanent residents (Green Card holders) awaiting availability of immigrant visas (Green Cards);
81. V3 Visa for the children of V1 Visa Holders and V2 Visa Holders;
82. WB Status* is an immigration status for temporary business visitors under the Visa Waiver Program; and
83. WT Status* is an immigration status for temporary pleasure visitors under the Visa Waiver Program, this includes vacation, tourism and medical treatment.

* Technically this is not a visa since they are under the Visa Waiver Program, but they are listed because they provide legal status in the USA, similar to a visa.

Source: US Department of State, 2018-2019