Immigration: Nonimmigrant (Temporary) Admissions to the United States [Updated September 10, 2019] [open pdf - 2MB]
From the Summary: "U.S. law provides for the temporary admission of foreign nationals. Nonimmigrants are foreign nationals who are admitted for a designated period of time and a specific purpose. There are 24 major nonimmigrant visa categories, which are commonly referred to by the letter and numeral that denote their subsection in the Immigration and Nationality Act (INA); for example, B-2 tourists, E-2 treaty investors, F-1 foreign students, H-1B temporary professional workers, J-1 cultural exchange participants, or S-5 law enforcement witnesses and informants."
CRS Report for Congress, R45040
Congressional Research Service: https://crsreports.congress.gov/