Hi Dawn
The Sodium pump is an active transport mechanism of substances in and out of cells using energy. It is also called the soduim potassuim pump as when soduim enters the cell potassuim is sent out. Also referred to as Ion pumps, Soduim potassuim ATPase, or soduim-potassuim exchange pump. You will find lots of information in biochemistry books, such as those written by Stryer, but may go in o far to much detail. Try searching for the above titles in basic anatomy and physiology books. A good one should give you the basics.
Hope this helps
Kat