The SAT & ACT are exams required by most (but not all) universities as a part of the admissions process.
Each exam is approximately 3 hours long and includes an optional (recommended) essay section (40-50 min).
Topics tested include:
Math: Algebra I & II, Arithmetic, Geometry, Basic Trigonometry, and Data Analysis
English: Grammar, Vocabulary in Context, Editing Skills
Reading: Reading Comprehension, Command of Evidence