Primary sources provide firsthand evidence gathered by the author(s). They may be created or documented at the time of an event, as in scholarly researcharticles, reports, letters, speeches, diaries, photographs,conference proceedings, and newspaper reports. A primary source may also be documented at a later time, such as autobiographies, interviews,memoirs, and oral histories...but these are still firsthand accounts.
Secondary sourcesdescribe, interpret or analyze information obtained from other sources (often primary sources). Examples of secondary sources include many books, textbooks, and scholarly review articles.
Tertiary sources compile and summarize mostly secondary sources. Examples might include reference publications such as encyclopedias, bibliographies or handbooks.
Note:
There are differences between the disciplines in the ways that source types are defined. See Virginia Tech's University Libraries for an excellent summary.
Defining a source as primary, secondary, or tertiary can also depend on how you are using the material. A newspaper article may be both primary and secondary. This example is from the University of Maryland:
A magazine article reporting on recent studies linking the reduction of energy consumption to the compact fluorescent light bulb would be a secondary source.
A research article or study proving this would be a primary source.
However, if you were studying how compact fluorescent light bulbs are presented in the popular media, the magazine article could be considered a primary source.
