What is a Primary source? Primary sources (or primary documents) are legal documents like legislation, cases, statutes (laws), regulations, parliamentary materials (bills, debates).
What is a Secondary source? Secondary sources are materials that discuss primary sources. This could include legal dictionaries or encyclopedias, books and articles.
Unless you are already familiar with the case or legislation you are researching it is often to begin with secondary sources as they will often cite relevant primary sources. Secondary sources also provide an expert's insights into your topic.
Please verify with your professor what citation style and version is preferred.