Before reading your last post....
CNA is certified nurse assistant and can be done in 2 weeks, less in some states, a little more in some states. CNA has other names in some states (Ohio, for one).
LPN is licensed practical nurse and usually takes a year or 18 months.
ADN is Associate degree in nursing and usually takes 2 years after certain prereq (prerequisite) classes.
BSN is bachelor of science in nursing and usually takes 4 years... two of gen ed (general education) and prereq and electives and two of nursing courses - although some schools spread the nursing courses into three years and expect the student to take some gen eds or electives while they take the nursing courses.
CNAs are not nurses, the other three are nurses. LPN, ADN and BSN are degrees. ADN and BSN (but not LPN) degrees allow a person to take the licensing exam - when the person passes then he is an RN (Registered Nurse). So, LPN is not an RN.
CNAs can do some of the same things nurses do...help people to the toilet, change briefs (diapers), feed people who need help eating, measure liquid input and output, change bedding (sometimes with the person in the bed), dress people, reposition people, take vitals (temperature, blood pressure, respiration, heart rate, weight), notice when something is wrong, shower them (in bed sometimes), brush their teeth, comb their hair, steady them as they walk, take them to other rooms, change some kinds of bandages.
LPN are licensed to do more things than CNAs are legally allowed to do. I'm not sure what.
RN are licensed to do everything CNAs and LPN do plus a whole lot more (ivs, foleys, accessments, educating the patient, more kinds of dressing changes,give medications, draw blood, and much, much more.
There is little difference between what an RN with a ADN is licensed to do and what an RN with a BSN is licensed to do. The difference is who hired them (in some areas of the country) and what they are hired for (in most/all parts of the country - a BSN can work all the jobs an ADN can but some jobs only a BSN has any chance of getting either because of the type of job it is (management for example) or because the employer prefers BSNs.
Many people become CNAs while in school for BSNs. LPN school is full time so it is very rare to do that at the same time as a BSN - although some people get an LPN so they can work as a nurse while they work toward their BSN.
After reading your last post.....
It depends, sort of. "Sort of" because the CNA is only 160 hours and it is easy hours for anyone who will be able to handle nursing school - mostly common sense, a little vocabulary, a few picky/precise prodecures to master... it isn't a big enough deal to concentrate on instead of BSN. You should be able to fit it into a summer or along with a light load one semester during the year and do it while you are taking classes.
If your school requires it or highly recommends it than obviously you will want to do it. If you can't get into other classes anyway, and you aren't sure you want to be a nurse or aren't sure what kind of nurse you want to be or want to gain some relevant experience or get your foot in the door somewhere for after you graduate than yes, it is a good idea.
If you have to give up a spot in something hard to get into (some schools give preference in their nursing programs to freshmen coming straight in from high school) to take the CNA - then it is obviously not a good idea.
If you don't expect to work as a CNA, then not so much of a good idea... it is never worthless when you are learning but it is probably not worth the cost.