To be accredited as a US medical school, a school must meet certain standards:
http://www.lcme.org/standard.htm
One of the criteria is as follows:
MS-8. A medical education program must develop programs or partnerships aimed at broadening diversity among qualified applicants for medical school admission.
Because graduates of U.S. and Canadian medical schools may practice anywhere in their respective countries, it is expected that an institution that offers a medical education program will recognize its collective responsibility for contributing to the diversity of the profession as a whole. To that end, a medical education program should work within its own institutions and/or collaborate with other institutions to make admission to medical education programs more accessible to potential applicants of diverse backgrounds. Institutions can accomplish that aim through a variety of approaches, including, but not limited to, the development and institutionalization of pipeline programs, collaborations with institutions and organizations that serve students from disadvantaged backgrounds, community service activities that heighten awareness of and interest in the profession, and academic enrichment programs for applicants who may not have taken traditional pre-medical coursework.
Every school is under the gun to recruit a diverse class. Failure to do so can result in sanctions by the accrediting agency (LCME).
Schools will offer scholarships (that needn't be paid back) and loans to help students cover the cost of attendance. Applicants who are highly desirable and highly sought after by a number of schools may attract more offers of free money. Generally these are students with rare qualities that are highly desirable. Some schools also offer some "need based" aid that need not be paid back as well as loans.
