"Primary sources are the raw materials of history — original documents and objects that were created at the time under study. They are different from secondary sources, accounts that retell, analyze, or interpret events, usually at a distance of time or place."
Library of Congress, Getting Started with Primary Sources
The Library of Congress provides a classic definition for primary sources as used in historical research. Taking the core concept of that definition, "created at the time under study" and combining it with the context of the research being pursued, can help to identify primary sources in other subject areas as shown on the Primary Sources/Secondary Sources guide
Articles published in different types of publications provide different kinds of evidence and knowledge, intended for different audiences. This chart suggests what to consider when determining what type of publication / article you have in front of you. Or that you may need to seek out.
Peer Review in 3 Minutes - this short video explains the peer review editorial process used by scholarly/academic journals.
The short video below will describe different types of scholarly articles.