SAT I (General Test) is a paper-based general test, assessing math, reading, writing, and language and essay skills. Most US Universities require SAT Scores for admissions. SAT I (General Test) is 3 hours and 50-minute multiple-choice test with the essay and 3 hours test without the essay. It has a validity of 4 years. SAT is scored out of 1600: a separate score of 800 each for Mathematics, Reading, and Writing while the essay is scored separately on a scale of 2 to 8. The optional Essay component of the SAT exam has been scrapped after June 2021.
Many universities also require students to take SAT-II (Subject Test). It has a validity of two years. Each SAT II (Subject Test) is of one-hour duration, scored out of 800. SAT II (Subject Test) is only required by top colleges. SAT II (Subject Test) is conducted for the following subjects: Literature, American History and Social Studies, World History, Math IC, Math IIC, Biology, Chemistry, Physics, and different languages like Chinese, German, French, etc. Check with your college whether they want it.
SAT II (Subject Test) has been scrapped after June 2021.