Historically, nurses were called "handmaidens" to physicians. However, a nurse's role has always had an important and separate role from physicians. Medicine and nursing complement each other, but can not replace each other.
Nurses are the primary observers in healthcare. But, more than observing, they act to prevent complications, control and reduce illness, and restore health. They also do patient teaching (and often educate new residents ;-)
Nurses operate under both a medical care plan by completing doctors' orders, but also function under a nursing care plan they create for each patient. They watch for common problems (such as after surgery) and develop a plan of care that addresses the whole patient. As the patient's condition changes, so does the nursing care plan and nursing actions. Within minutes, a nurse can go from administering routine medications and IVs to dealing with a medical crisis to dealing with a code to comforting family or reassuring them through education about what is happening to a loved one. In direct patient care, nurses can change a bed as easily as changing a surgical dressing with sterile technique, or teach a new diabetic how to give self-injections as easily as titrating medication in an IV.
Without nurses, patients would lie in their own urine or feces without being changed; would suffer needless pain, complications, fear, etc. Without nurses to teach aspects of self-care, patients would more often return to hospital care due to preventable complications. Without nurses teaching aspects of normal anatomy, more patients would still believe mistaken information or feel confused about what is happening inside the body. Without nurses to answer patient's questions, more patients would worry more about insignificant symptoms but possibly ignore more important ones.
Nurses work in many areas, from school or community health to hospital wards to nursing homes to prisons. In hospitals, nurses staff all usual areas from the ER to medical or surgical wards, to spinal recovery and rehab. Skilled nurses work around the clock to save lives in cardiac wards, ICU, and NICU for premie babies. Without the hands-on and skilled nursing care, more lives would be lost in all institutions that employ nurses.
And, for nurses who are moms and dads, they put band-aids on their kids better than anyone! :-)