When doing research, sources are categorized in three types:
Primary sources are firsthand accounts of events or periods of time, as well as original research and data.
Examples: diaries, photographs, scientific research
Secondary sources are interpretations, discussions,and analysis of primary sources. They are used to gain a broader understanding of the subject.
Examples: articles, magazines
Tertiary sources analyze, synthesize, and report on secondary sources. They are often written for a general audience.
Examples: textbooks, encyclopedias, Wikipedia