Secondary source is created after an event and is based on primary sources. It helps explain or interpret what happened in the past. Secondary sources are widely used in education.

Textbooks, documentaries, and articles are common examples. A historian may study letters, photographs, and records, then write a book explaining those events. These sources often combine information from many primary sources.

Secondary sources are found in books, websites, and classrooms. They are used to organize and explain historical information.