"Primary sources are original materials. They are from the time period involved and have not been filtered through interpretation or evaluation. Primary sources are original materials on which other research is based. They are usually the first formal appearance of results in physical, print or electronic format. They present original thinking, report a discovery, or share new information."-University Libraries, University of Maryland
Examples: Artifacts, Images (Photographs or Works of Art), Works of Literature, Interviews or Oral Histories, Newspaper Articles written at the time, etc.
"Secondary sources are less easily defined than primary sources. Generally, they are accounts written after the fact with the benefit of hindsight. They are interpretations and evaluations of primary sources. Secondary sources are not evidence, but rather commentary on and discussion of evidence."-University Libraries, University of Maryland
Examples: Biographies, Commentaries, Histories, Criticisms, etc.
"Tertiary sources consist of information which is a distillation and collection of primary and secondary sources."-University Libraries, University of Maryland
Examples: Encyclopedias, Dictionaries, Bibliographies, Almanacs, etc.