They may send a “likely” letter, usually AFTER they receive your application, around February/early March. In this letter, an admission officer will tell you he/she is going to recommend you for admission to the committee and check if you are still interested. Some schools, like Harvard, may also call around the same time (do not confuse a “likely” call with an alumni call for an interview). All other communications you receive, starting sometimes in your sophomore year, is basic “marketing”. My daughter received tens of email and letters by mail from very prestigious schools such as Columbia, University of Chicago, UPenn, Brown etc… She resisted applying to most of these schools, but “fell” for Columbia and UPenn, only to be denied, of course!