This video from the University of Victoria Libraries describes the difference between primary and secondary sources.
People use original, first-hand accounts as building blocks to create stories from the past. These accounts are called primary sources, because they are the first evidence of something happening, or being thought or said.
Primary sources are created at the time of an event, or very soon after something has happened. These sources are often rare or one-of-a-kind. However, some primary sources can also exist in many copies, if they were popular and widely available at the time that they were created.
All of the following can be primary sources:
From Library and Archives Canada
Secondary sources usually analyze or examine events or issues. Secondary sources include books or articles written by researchers who study subjects but who are not directly involved in the original events or issues which they study. Secondary sources are often written after the events or issues in question, and may include discussion of primary sources.
Some examples of secondary sources include:
Scholarly articles
Newspaper or magazine articles looking back at an event (for example, a retrospective on the 100th anniversary of the sinking of the Titanic)
Biographies
Textbooks
Encyclopedias