Primary sources contain original information that has not been filtered or interpreted. The information can exist as a physical object or in print or electronic formats. Often primary information is the first official appearance of a given result or idea.
Whether a piece of information is considered to be primary can vary between subject areas. In the sciences, examples would include numerical data, original findings or ideas printed in research articles from scholarly journals. In the humanities, it could be any objects or documents created during a certain time period. These can include artifacts, paintings, maps, diaries, letters, sound recordings, case studies and surveys.
Information also can be considered secondary or even tertiary sources. Any source that comments on or evaluates the primary information can be considered secondary. This provides the filtering or interpretation that is absent in a primary source. Examples of secondary sources can be bibliographies, criticisms, encyclopedias or textbooks.