What colleges want actually isn't all that complicated:
1. Students who enjoy learning and are excited about doing more of it in college.
2. Applicants who will become a part of the campus community, like playing saxophone in the marching band, doing improv with the drama club, or staying up late doing physics problem sets with fellow future Nobel Prize winners.
3. Students other people will like being around.
That's pretty much it.
Everything in the college application process, from transcripts to applications to essays to interviews, is designed so colleges can look for evidence that you would do those three things if you were admitted.