Primary Sources: The artifact/object of study (the actual text of the play, hat that someone wore in the 1940s, the painting that sits in the museum). Think of primary sources as objects that sit on those pedestals in museums or behind display cases.
The stories, ideas, people, events (the actual text of the bible) is the primary source.
Secondary Sources: Sources that critique, interpret, or try to understand the primary source (scholarly articles, books, interpretations). Think of secondary sources as those experts that sit in the room and explain the item on the pedestal.
Here is an example of a secondary source. The author is using historical events to find meaning in the books of Genesis and Exodus (click on image to enlarge).