I agree with other posters that whether and how much APs matter for admissions is highly dependent on the colleges.
Some core AP courses are viewed as among the most rigorous and challenging courses if your HS (except for a few that are known to offer more challenging courses) offer them. How students challenge themselves in HS and how well they do in challenging situations is an important part of college admission evaluation for nearly all selective colleges.
Among the set of core AP courses, which ones will matter more depends on what you want to study in college. You’re expected to take the ones that are most relevant to your intended area of study in college for the highly selective colleges, if your HS offers them.
For the colleges where APs are an important part of their admission evaluation and most of their applicants have taken APs, having high AP scores (for AP courses taken prior to senior year) is an important indicator that the student has done well in those courses (especially if s/he is from a HS where course rigor is less well known and/or grade inflation is apparent). Conversely (and this is probably somewhat controversial), some colleges may view the lack of AP scores in the same core AP courses that are more relevant to the student and taken prior to senior year negatively, in the absence of evidences that show the student couldn’t take the exams.