CNA = Certified Nursing Assistant. You don't have to become a CNA to enter the nursing world, but it would give you a good exposure to working with patients and using medical terminology
LPN/LVN = Licensed Practical Nurse/Licensed Vocational Nurse. This is generally a one year course, although it may take a bit longer. In many regions, LPNs are not hired to work as hospital nurses and work in long-term care facilities (nursing homes) or clinics instead. Some people start out as LPNs and then work to complete an RN degree.
RN = Registered Nurse. ADN/ASN nurses have an associate's degree. This takes a minimum of two years to complete. Diploma nurses generally complete a three-year program. BSN nurses have a four-year degree. ADNs and diploma nurses can take completion programs that will give them a BSN (bachelor's degree), and many do so while they are working as nurses and take advantage of tuition reimbursement programs through their employers
All LPN/LVNs take the NCLEX-PN test after they graduate from their program to qualify as an LPN/LVN.
All RNs, no matter how much education they have, take the NCLEX-RN to qualify as an RN.
Some RNs choose to pursue a master's degree--MSN--so they can teach or go into advanced practice.
A few will go on to get a doctorate in nursing.
That's the ladder.
Hope this helps.