A secondary source might be a book such as a biography.
People tend to confuse secondary sources with primary sources. Let’s first look at the distinction. The best way to think about a primary source is a firsthand account that can take the form of an interview, a photograph, audio/video recordings, survey data, and even an autobiography. A primary source can be thought of to be “straight from the horse’s mouth,” so to speak. A secondary source can be an interpretation or analysis found in books or journal articles. It’s important to note that even though a book or journal article may contain quotations of primary sources as would a biography, it would still be considered secondary because it would not have been written by the source of information; rather, it is a secondhand account.