Primary sources are raw data; original sources of information 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.
Sources that analyze or interpret primary data. Secondary sources are not evidence, but rather commentary on and discussion of evidence. However, what some define as a secondary source, others define as a tertiary source.
Tertiary sources consist of information which is a distillation and collection of primary and secondary sources.