Eligibility for need-based grants is often determined by calculating how much you and your parents can reasonably contribute to fund your education and subtracting this from the expected cost of attendance at your college or university. Student's total household income will usually need to be below a certain threshold for this type of grant, however, so you may not qualify even if there is gap between expected family contribution and cost of attendance. This is the type of grant most commonly given by federal financial aid sources, including Pell Grant.
Minority grants are scholarships, usually administered by private organizations, which require applicants to have certain ethnic backgrounds to qualify. The largest of these are available for students who have traditionally not had much opportunity for higher education. Many minority grants will also have other qualifications, such as grants for low- to moderate-income minority students, or minority students interested in a certain field of study.
There are a large number of grants available through both government and private organizations that require the student be interested in a certain subject or career path to qualify. The most popular of these are grants for people receiving training in particularly high-demand fields like teaching in public schools or health care and nursing. Grants and scholarships for students interested in less high-demand fields of study and career paths are also available, though these tend to be more competitive.
While this can refer to minority grants, there are a good deal of other grants for students with specific backgrounds. This can include grants in which the student who meets certain qualifications is guaranteed some amount of funding, like the Transfer Entitlement Cal Grant, which provides funding to California students transferring from community colleges to four-year universities, or scholarships to help single mothers pay for tuition.
To qualify for merit scholarships, you must meet certain academic qualifications or have some sort of outstanding achievements. Often these will have a minimum grade point average qualification, and may incorporate elements from other types of grants, like scholarships for minority honor students. In addition to minimum academic requirements, merit scholarships may require applicants to complete an essay or submit letters of recommendation.