For a good explanation of Secondary Resources check out these links:
Historiography examines a collection of historical writings on a particular topic and analyzes the different approaches to and interpretations of the topic. It also recognizes the major thinkers and arguments surrounding the topic as well as any major changes that have risen in approaching the topic over time.
Historiography operates as a dialogue between historians that emphasizes the main points of the discussion and informs the reader of the most important facets of the dialogue and in this way demonstrates the author's authority on the topic.
It is important to become familiar with your topic on a broader scale. Your historiography should then establish and connect the major thinkers and arguments on your topic.
(adapted from: http://www.trentu.ca/history/workbook/historiography.php)