Any student who wants to apply to a college or university in the United States will certainly need to take the SAT or ACT, since most require the student to submit test scores during the application process.
In the process of admission, your ACT scores will be reviewed alongside your high school GPA, the classes you took in high school, letters of recommendation from teachers or mentors, extracurricular activities, admissions interviews, and personal statement.
The ACT provides colleges with one common data point that can be used to compare all applicants. Overall, the higher you score on the ACT, the more options for attending and paying for college or universities will be available to you.