A primary source is original information about an event, person, object, product, or work that is not accompanied by analysis, opinion, or commentary.
For example, a news report about a hurricane was created by a newspaper reporter. The reporter was an eye-witness who was on location and reported facts about the storm. The report is a primary source. It was created at the time of the event and only reported the facts.
Years later, an documentary film discusses the historical economic impact of the hurricane on a nearby town and includes the original news report. The news report itself is a primary source. The film's discussion and analysis of the hurricane makes the film a secondary source.
A secondary source is an interpretation of a primary source. For example, if your professor asks you to view a film and then write a paragraph about it's meaning to you, the film is the primary source, while your personal interpretation of the film is the secondary source.
Examples of secondary sources that contain interpretations/analyses include: