This is a pretty open-ended question, and the answer really varies depending upon what you want to do and what type of nursing that you want to get into. There are a lot of people who choose to become a CNA (Certified Nursing Assistant) first before any other type of nursing specialty because it typically takes the shortest amount of time (compared to other things like becoming an RN) and it gives people a chance to understand what nurses do, and whether or not they'll like the field. If someone becomes a CNA and doesn't like it, they typically will not have spent as much time preparing as if they became an RN and then decided on a career change.
Regardless of which nursing specialty you're considering, there is typically an educational requirement, as well as some prerequisites and testing that needs to be completed. For Certified Nursing Assistants, this usually means undergoing a background check, making sure your immunizations are current, and then attending a qualified program. Generally speaking, the Department or Board of Nursing in your state will have a list of programs that are approved for CNA training or at least be able to provide you with some direction.
After completing a CNA course, you'll then need to take the state CNA exam and once you pass that and have completed any other objectives, you'll then generally be considered to be a CNA. If you want to become a Registered Nurse, this process is a bit more involved because you'll typically need to attend at least a couple years of school and complete clinicals (which are somewhat like an internship), and you'll also have to pass the NCLEX nursing exam. This generally takes at least two years, but can take more if you want to get a BSN. As with any career, that are a lot of steps and things that you need to understand before you get started. In nursing, because you need to be qualified to take care of patients, you'll have to definitely spend some time training and studying, as well as passing various nursing exams.
No matter where a nurse or CNA works, they are important! Nurses are often some of the most important people on any medical team becauset they keep things together and running smoothly. They are often the first and most frequent point of contact with patients.
One of the most common places for nurses and CNAs to work in in a hospital setting. They will often help patients with wound care and a variety of other needs in situations like this, including transporting patients and more.
Whether it's blood pressure, height, weight, body temperature, or some other type of medical measurement, nurses and sometimes CNAs are often the people who take these measurements and then recored them.
It's almost a universal requirement that nurses and CNAs know both basic first aid techniques and also CPR so that they can respond to patient injuries or other situations that might require CPR or some other type of medical assistance.
If you're interested in learning more about nursing, check out some other links below. Hopefully you'll find some of this information to be both helpful and informative.
Nursing Assistants & Orderlies - The Bureau of Labor Statistics
The Bureau of Labor Statistics official page on Nursing Assistants.
Wikipedia's - Nursing Assistants
Wikipedia's official entry on nursing assistants.
Nursing Associations by State - Nurse.org
A comprehensive list of nursing assotiations by state.
The National Student Nurses Association - nsna.org
The offical site of the National Student Nurses Association (NSNA).