The SAT is the most widely taken standardized entrance exam in the United States. It's administered to approximately 1.8 million students throughout the year. Students usually take the test in the spring of their junior year and/or the fall of their senior year in high school.
Standardized tests like the SAT are designed to allow college admissions officers to judge all students by a common measure; these tests compensate for the disparity in high school grades because of the many differences between the thousands of schools in the United States such as grade inflation and quality of teaching. They are designed to predict your academic performance as a college freshman. The SAT tests math, vocabulary, and reading knowledge and skills.
Check with the universities that interest you to find out the average SAT score of that school. Also, depending on which schools you apply to, and the specific programs that appeal to you, you may also have to take what used to be called Achievement Tests, but are now called SAT II Subject Tests. These exams give you a chance to show off your knowledge and skills in specific subject areas.
Because the SAT is an important element of the college admissions process, preparation can improve your score.