Source: https://www.hooyou.com/b1-visa/b2-activities.html
Timestamp: 2019-04-23 22:49:29+00:00

Document:
Tourism or Family Visits: B-2 visa status is granted to aliens traveling to the US as tourists or to visit family or friends.
Medical Reasons: Aliens coming to the US to receive medical treatment are eligible for B-2 visa status.
Participation in Social Events: Aliens may travel to the United States under B-2 visa status to participate in conventions, conferences, or convocations of fraternal, social, or service organizations.
Armed Forces Dependents: B-2 visa status can be granted to dependents of an alien member of any branch of the US Armed Forces temporarily assigned for duty in the United States.
Dependents of Crewmen: B-2 visa status can be granted to alien dependents of D visa crewmen who are coming to the US for the sole purpose of accompanying the principal D visa holder.
Aliens Attending a Short Course of Study: Aliens coming to the US primarily for tourism are also allowed to partake in a short course of study.
Amateur Entertainers and Athletes: An amateur is by definition not a professional in their activity. Therefore, an amateur is someone who normally performs the activity without payment. An amateur (or group of amateurs), who will not be paid for any performances they make, may perform in the US for social/charitable reasons or as a competitor in a talent show, contest, or athletic event under B-2 visa status.
To renew a relationship with the prospective spouse.
Proxy Marriage: An alien spouse married by proxy to another nonimmigrant alien, currently in the US, can be granted a B-2 visa to join said spouse. After arrival, the joining spouse must apply with DHS to gain permission to change to the appropriate derivative nonimmigrant status after the marriage has been consummated.
The Spouse or Child of a US Citizen or Legal Permanent Resident: An alien spouse or child, including adopted child, of a US citizen or permanent resident may come to the US to accompany or follow to join the spouse or parent for a temporary visit.
Cohabitating Partners, Extended Family Members, and Other Household Members not Eligible for Derivative Status: The B-2 visa classification is appropriate for aliens who are members of the household of another alien under a long-term nonimmigrant status but who is not eligible for derivative status under the relevant long-term visa classification. B-2 status can also be given to alien members of the household of a US citizen who generally works overseas but must return to the US for a temporary period.
Aliens so eligible include, but are not limited to: cohabitating partners or elderly parent(s) of temporary workers, students, diplomats, and accompanying parents of a minor F-1 student.
B-2 classification can also be given to a spouse or child who qualifies for derivative status (other than derivative A or G) but for whom it may be impossible or inconvenient to apply for H-4, L-2, F-2, or other appropriate derivative statuses.
The alien must intend to maintain a residence abroad and otherwise meet the qualification for a B visa.
Such aliens who plan to stay in the US for more than 6 months should ask for a one-year extension of stay from the Department of Homeland Security upon their admission. They may subsequently apply for extensions of stay for the duration of the principal alien’s status in increments of 6 months.
Aliens Seeking Naturalization under INA § 329: An alien who is eligible for benefits under INA § 329, and who wishes to enter the US to take advantage of such benefits, may be granted a B-2 visa. For a further explanation of B-2 visas for those who can naturalize under INA § 329, especially for children that are so eligible and for the dependents of those so eligible for naturalization under INA § 329, please refer to 9 FAM § 31.31 N14.5-14.7.
Neither the list above nor that provided by 9 FAM § 31.31 N13-14 is exhaustive. However, if the activity you plan to undertake is not directly mentioned in the list provided by 9 FAM § 31.31 N13-14, there is a chance your petition for a B-2 visa will be denied. B-2s are most often issued for tourism, visiting friends and family, to receive medical treatment, or to participate in social events.

References: § 329
 § 329
 § 329
 § 329
 § 31
 § 31
 § 31