Health Informatics is a wide field and consists of subfields and was previously known as Medical Informatics. The new coinage - Health Informatics was brought about to embrace other aspects of health that might not be neccessarily be medically related. In one sentence, Health Informatics is the gathering, analysing and organizing of health related information using current information technologies. It is a specialized field, made up of several subspecialties, including nursing informatics. There are various resoucrces out there that are better in giving a better explanation than I. You could try this site http://www.biohealthmatics.com but if it does not provide you with the answers you require, I would happy to find out more for you. Just let me know exactly what you are looking for.