In order to understand a primary sources, it often makes sense to first think about what a secondary source is. An encyclopedia article about Cesar Chavez based upon photos, journals, and newspaper articles from a time period is a secondary source. The source material for the article (the photos, journals, and newspaper articles) are the primary sources.
What are example of primary sources?
*books, newspapers and magazine articles (could be the text only does not have to be original content or even a photocopy)