Here are definitions used by the Smithsonian Archives:
Primary sources are documents or objects created as part of daily
life - birth certificates, photographs, diaries, letters, etc.- or reports
from people directly involved in the subject.
Secondary sources are documents that interpret, analyze, or synthesize
information, usually produced by someone not directly involved in the
subject.
Which are more reliable? A student/researcher needs to learn how to assess a creator's or recorder's bias and then make judgments about reliability.
Primary historical sources are:
Records of events described or recorded by
someone who participated in / or witnessed the events, or who got their
information from others who did.
Format: newspapers,
documents, letters, diaries, notebooks, interviews, and contemporaneous
news accounts, or any piece of information that is used for
constructing history such as artifact of its times.
"They provide the intimacy and the immediacy of an on-the-scene
perspective that cannot be recaptured in distant, often re-filtered and
reinterpreted history. The thesis is often less of stated proposition
and more of a subtle revelation."
