The SAT is an entrance exam used by most colleges and universities to make admissions decisions. It is a multiple-choice, pencil-and-paper test administered by the College Board.
The purpose of the SAT is to measure a high school student’s readiness for college, and provide colleges with one common data point that can be used to compare all applicants. College admissions officers will review standardized test scores alongside your high school GPA, the classes you took in high school, letters of recommendation from teachers or mentors, extracurricular activities, admissions interviews, and personal essays. How important SAT scores are in the college application process varies from school to school.
Overall, the higher you score on the SAT and/or ACT, the more options for attending and paying for college will be available to you.