The USCIS provides the definition and procedure for obtaining "B" nonimmigrant visas, which is cited below. Please note that it is the State Department, not the Homeland Security Office, which is in charge with visas for traveling into the U.S.
"B" Nonimmigrant Visas - Visitor Visas for Business and Pleasure
The "visitor" visa is a nonimmigrant visa for persons desiring to enter the United States temporarily for business (B-1) and for pleasure or medical treatment (B-2). As examples, if the purpose of your planned travel is recreational in nature, including tourism, amusement, visits with friends or relatives, rest, medical treatment, and activities of a fraternal, social, or service nature, then a vistor visa (B-2) would be the appropriate type of visa for your travel. As additional examples, if the purpose for your planned travel is to consult with business associates, travel for a scientific, educational, professional or business convention, or conference on specific dates, settle an estate, or negotiate a contract, then a business (B-1) visitor visa would be the appropriate type of visa for your travel.
Foreign travelers who are citizens from certain eligible countries, may also be able to visit the U.S. without a visa on the Visa Waiver Program.
Qualifying for a Visa
Applicants for visitor visas must show that they qualify under provisions of the Immigration and Nationality Act. Applicants must demonstrate that they are properly classifiable as visitors under U.S. law.
The presumption in the law is that every visitor visa applicant is an intending immigrant. Therefore, applicants for visitor visas must overcome this presumption by demonstrating that:
The purpose of their trip is to enter the U.S. for business, pleasure, or medical treatment;
That they plan to remain for a specific, limited period;
Evidence of funds to cover expenses in the United States;
Evidence of compelling social and economic ties abroad; and
That they have a residence outside the U.S. as well as other binding ties which will insure their return abroad at the end of the visit.
Where Do I Apply for a Visitor Visa?
Applicants for visitor visas should generally apply at the American Embassy or Consulate with jurisdiction over their place of permanent residence. Although visa applicants may apply at any U.S. consular office abroad, it may be more difficult to qualify for the visa outside the country of permanent residence.