primary and secondary sources
Information can typically be broken down into two categories: primary, and secondary.
Primary sources are sources of original information and interpretation. These sources were written, created or otherwise produced during an experience or time period, and present a first hand, or eye-witness account of an event by a participant or observer. These may include journal articles reporting empirical research, data, diaries, photographs.
Secondary sources are those that interpret, analyze or summarize previously presented materials, be they original, primary sources, or more recent secondary sources. They tend to provide a broader perspective, and give context to those materials that they review. Secondary sources include textbook integration and interpretation of primary research articles, encyclopaedias, journal review articles, and even lecture notes.