Difference between primary law and secondary law?

A primary authority is a document that establishes the law on a particular issue, such as a case decision, Constitutions, Statutes, Rules of court procedure, Rules of evidence, Treaties and ordinances.

In law, a secondary authority is an authority purporting to explain the meaning or applicability of the actual verbatim texts of primary authorities such Law review articles, comments and notes (written by law professors, practicing lawyers, law students, etc.)

Source:

http://en.wikipedia.org/wiki/Secondary_authority

http://en.wikipedia.org/wiki/Primary_authority

http://definitions.uslegal.com/p/primary-authority/