Most colleges and universities require students that apply to take the SAT or ACT and provide their scores as a part of their application. The SAT and ACT are both standardized exams that demonstrate college readiness and test students on their math, science, English, grammar, and writing skills. Students can usually choose to take one or both of the tests. It is widely recommended that students study and practice for the SAT and ACT before taking them, as well as take their exam of choice multiple times in order to achieve the highest score possible. Below are some resources with information on the exams as well as free and paid practice options.
Khan Academy is a great resource for SAT practice, as their program is free and offers personalized help with the sections and sub categories that you struggle with. https://www.khanacademy.org/sat