Connecting with faculty and current students will help you better understand the school, programs of study, culture, expectations, opportunities, etc. But beyond helping you make informed application decisions, preliminary "networking" can help you get admitted.
You want to make yourself known (a household name, if you will) so that when your application crosses the admissions officers’ desks, they go, "Oh, I remember X! They’re super passionate about researching Y!" You may even end up with faculty members pushing for admission on your behalf. So don’t be shy: reach out to faculty members.
Another important point: it’s very likely that you will be required to find a graduate supervisor before applying to a program.