This is a number assigned to every ERIC document to identify which of the ERIC Clearinghouses (departments) indexed this record. The Clearinghouses do more than index journal articles, but also provide other materials relevant to their area, such as books, lesson plans, and discussion groups. For example, this record came from the Information and Technology Clearinghouse--the IR at the beginning of the number tells you this. A visit to their website will quickly show you what they have to offer on this topic, http://www.ericit.org/
If you are interested in learning more about ERIC Clearinghouses click here.