The ACT exam is a standardized test used for college admissions that consists of four multiple choice sections - English, Math, Reading, and Science - and an optional writing test. It is accepted by all four-year colleges and is more popular than the SAT exam in the Midwest and Southern US, while the SAT is more popular on the east and west coasts. Colleges consider the ACT score alongside other criteria like class rank, GPA, and extracurricular activities for admissions decisions.