Secondary sources interpret or analyze primary sources. Thus, they are a step removed from the event or original text. Examples of secondary sources include:
How you use a source determines whether it is a primary source or secondary source. If you are analyzing a magazine article from the 1940s to talk about what life was like during that time period, it is a primary source. However, if you are citing information from a magazine article written today about the 1940s, then it is a secondary source.