Hi all, long time reader first time poster.
I'm about to grad (11/06) from an ASN program, and due to my experience in EMS, I got hired in the NICU of a well respected hospital. In this area there is the labor and delivery department first, then the "mother baby" unit, which includes the nursery. The Neonatal Intensive Care Unit (NICU) is where, as previously stated, babies who are very sick go to be cared for under special circumstances by specially trained RN's and neonatal intensivists (specializing MD's). The next level is for babies who are older than 1 day -- those who leave the hospital for ANY amount of time, go home, and return -- is the pediatrics department. That includes the PICU (pediatric ICU), as well.
I hope that helps... continue your education, and take advantage of EVERY clinical experience you get in nursing school, you'll have many opportunities to see different departments, and while learning, decide where you want to work! Feel free to ask any other questions, we're all here to help.