Reference resources are usually encyclopedias, dictionaries, handbooks, manuals and other books that you would refer to when wanting to know a definition of a word or concept, a general overview of a topic, specific information about a certain period of time or event in history.
CRJ101 Course Tip: The first step in researching a topic (in this example, "restorative justice") is defining it. Often encyclopedias will lead you to the most relevant court cases or public laws in addition to giving you a broad understanding of your topic. Read the entry and look for cases (471 U.S. 1) or public laws (The Violent Crime Control and Law Enforcement Act of 1994).