Primary sources are original materials on which other research is based.
They are from the time period
involved and have not been filtered through interpretation or evaluation.
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.
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.
However, what some define as a secondary source, others define as a tertiary source. Context is everything.
Tertiary sources consist of information which is a distillation and collection of primary and secondary sources.