It
is all very confusing, isn't it?

There are three routes of preparation in nursing -- diploma schools (typically hospital-based, 2-3 years), AD degrees (community college degrees), and BSN degrees (standard undergraduate college/university degrees). All three types of programs get referred to as "nursing school," and all three prepare you to take the NCLEX-RN, the licensure exam for RNs. Once you pass the NCLEX, you are eligible to be licensed to practice as a registered nurse in a particular state. Once you get a license,
then (and only then!) you're an "RN."
Does your present college/university have a nursing program? If you are already a sophomore bio major, you may be in a good position to transfer into their program (and finish at about the same time you would have finished your bio degree). If not, your best bet is probably to talk to the people at
all the various nursing programs in your area and see what they have to offer you and which one would be a good match for you. Different programs require different prerequisites (many of which you may have already taken as a bio major) and take different amounts of time (and $$). Although a BSN offers some more professional opportunities than an AD degree or diploma, whether or not that matters to you is a v. personal decision. Also, there are many "RN to BSN" programs out there that enable AD or diploma grads to take just the courses necessary to complete a BSN degree -- many people who intend to eventually take a BSN degree start out by going the quickest route available to them (diploma or AD) and finish the BSN later, after they are licensed and employed. Again, that's a v. personal decision -- no one else can tell you what is the best choice for
you.
As for what you do after nursing school, if you
choose to continue your education beyond the basic preparation in nursing, there are many graduate programs (Master's and doctoral programs) that prepare you for advanced practice nursing (nurse midwives, nurse practitioners, nurse anesthetists, and clinical nurse specialists) and/or scholarship/research.
There are many, many different specialities and opportunities, as well as a lot of career flexibiliity, available in nursing (which are some of the reasons it appeals to many of us). Best wishes with your journey --