Popular - Written by professional journalist for the general public. Sources are cited in passing, but not formally. Editorially reviewed for grammar, not necessarily content.
Scholarly - Written by researchers or scholars in the field for other researchers and scholars. Always contain references and footnotes.
Primary - created as close to the original event as possible. Examples: photography, video, speech, data from an experiment.
Secondary - based on, or about, a primary source. Examples: articles or books that are based on or interpret the event.
Tertiary - Sources that summarize / synthesize the information in secondary sources. Examples: textbooks, references sources like encyclopedia.
Peer-reviewed sources have been vetted by people who are authorities within their field of scholarship. When academic journals are considering publishing an article, a panel of scholars assess the quality of the article.
See example from ProQuest:
Now you have your sources! Use the following writing tips to comprise your paper: