Primary sources can provide first-hand testimony or direct evidence concerning a topic under investigation. They are created by witnesses or recorders who experienced the events or conditions being documented. Often these sources are created at the time when the events or conditions are occurring, but primary sources can also include autobiographies, memoirs, and oral histories recorded later. Primary sources are characterized by their content, regardless of whether they are available in original format, in microfilm/microfiche, in digital format, or in published format.
Examples:
Secondary sources offer an analysis or a restatement of primary sources. They often attempt to describe or explain primary sources. Some secondary sources not only analyze primary sources, but they also use them to argue a contention or persuade the reader to hold a certain opinion.
Examples:
A journal/magazine article which interprets or reviews previous findings.
Most books are secondary sources, where authors reference primary source materials and add their own analysis.
Tertiary sources consist of information which is a distillation and collection of primary and secondary sources.
Examples:
Dictionaries
Encyclopedias
Manuals
Guidebooks