A secondary source is usually a professional or closely-related person to an incident. For example, take the September 11 attacks on the World Trade Center.
Primary Source: Survivor from the buildings, a diary, a phone call recording from someone inside the planes.
Secondary Source: Child of a victim, a firefighter, a news outlet.
Tertiary Source: Unbiased outside perspective, such as a textbook.
Utilizing secondary sources adds a layer of comprehension and relating to the reader.
