The B-1 visa is for visitors who are coming temporarily to the United States for business purposes, such as consulting with associates or attending a conference. The B-2 visa is for visitors who are coming temporarily to the United States for pleasure or tourism.
Visitors from some countries are permitted to enter the United States without a visa stamp in their passport. These visitors are admitted as B-1/B-2, but under the "Visa Waiver" program.
B-1 and B-2 visas are not intended for people who plan to work or study in the United States. You are prohibited from these activities while in the country on a B-1/B-2 visa, and it can be tough to change your status.
A B-1/B-2 visitor may receive an honorarium and reimbursement of expenses for giving a lecture or presenting at a conference as long as they are at Saint Louis University for no more than nine days and have not accepted similar payments from more than five other institutions in the previous six months.
While you’re at Saint Louis University, you may have friends or family from back home who want to visit you. Your visitor(s) will probably need B-1 or B-2 visas, and it may help to provide them with a copy of your paperwork (visa, I-20, enrollment letter from SLU, etc.). You do not need a letter of invitation from the Office of International Services for friends and family to visit. Providing family members with a letter of invitation will not improve their chances of obtaining a visa. The success of the applicant's request for a visa is dependent upon their ability to prove that they have no intention of staying permanently in the United States.
Review the website of the U.S. embassy or consulate where your visitor(s) will apply for their visas for country-specific instructions. This is the best source of detailed information for the steps they must take and the documents required to obtain a visitor visa.