A-2 Other foreign government official or employee, and members of immediate family. INA Section 101(a)(15)(A)(ii) 8 CFR 214.2(a)

A-3 Attendant, servant, or personal employee of A-1 and A-2, and members of immediate family. INA Section 101(a)(15)(A)(iii) 8 CFR 214.2(a)

Visitors Business or Pleasure Visitors
Tips for U.S. Visas – Business or Pleasure Visitors

B-1 Temporary visitor for business INA Section 101(a)(15)(B) 8 CFR 214.2(b)

B-2 Temporary visitor for pleasure INA Section 101(a)(15)(B) 8 CFR 214.2(b)

Visa Waiver Program Visa Waiver Program (Immigration.gov)
Visa Waiver Program (Dept. of State)

Aliens in Transit

C-1 Alien in transit directly through U.S. INA Section 101(a)(15)(C) 8 CFR 214.2(c)

C-1D Combined transit and crewman visa INA Section 101(a)(15)(C) & (D) 8 CFR 214.2(c)

C-2 Alien in transit to UN headquarters district under Section 11.(3), (4), or (5) of the Headquarters Agreement INA Section 101(a)(15)(C) 8 CFR 214.2(c)

C-3 Foreign government official, members of immediate family, attendant, servant, or personal employee, in transit INA Section 212(d)(8) 8 CFR 214.2(c)

C-4 Transit without Visa, see TWOV INA Sections 212(d)(3), and 212(d)(5) 8 CFR 212.1(f)

Crewmen

D-1 Crewmember departing on same vessel of arrival INA section 101(a)(15)(D) 8 CFR 214.2(d)

D-2 Crewmember departing by means other than vessel of arrival INA section 101(a)(15)(D) 8 CFR 214.2(d)

Treaty Traders and Treaty Investors Instructions for Form I-129: Petition for a Nonimmigrant Worker

E-1 Treaty Trader, spouse and children INA Section 101(a)(15)(E)(i) 8 CFR 214.2(e)(1)

E-2 Treaty Investor, spouse and children INA Section 101(a)(15)(E)(ii) 8 CFR 214.2(e)(2)