Not all colleges are the same. Some schools have very high admissions standards.
Some schools receive far more applicants than they can take.
Some schools accept almost anyone who applies. You need to know which of these statements apply to each of the colleges you are interested in applying to. You have done a self-assessment and selected a set of colleges to research. You have learned all you can about the colleges and you know how you stack up compared with students that the colleges usually admit. Now you need to narrow your choices down to a handful of colleges that you will actually apply to.