Peer review is the process by which articles or other works are critiqued before they are published. Authors send articles to an editor, who decides whether the work should be forwarded to reviewers for the journal. The most stringent form is anonymous or blind review, where neither the author nor the reviewers know whose work is being examined by whom. This helps reduce bias.
Reviewers are usually well-published researchers and experts. They return the articles to the editor with remarks and recommendations-- usually publish as is (rare), publish if edited or changed in specific ways, or don't publish. Editors most often go with the recommendation of the majority of the reviewers.
The process is intended to improve the studies published-- more eyes on a project, and one's reputation on the line with peers, tends to improve the quality of what's published. There are cases where it hasn't worked, and critics of the peer review cycle (some claim that it limits innovative studies, among other issues), but it is the best system that has been developed to this point.
Not all scholarly journals are peer-reviewed, but many are.
("Peer-Reviewed/Scholarly" was created at the University of Arkansas University Libraries. Permission to use this content was given by Necia Parker-Gibson).
What is considered a primary source varies somewhat by discipline. In any case, think of a primary source as first-hand knowledge, eyewitness accounts, reports or testimony about (X topic).
In the sciences, a primary source is the first report of research, published as a journal article, a research report or conference proceeding, or if extensive, a book or book chapter. They include methodology, data and results, and discussion.
In social sciences, such as anthropology, ethnography, psychology, sociology or social work, a primary source may be the first report of research, especially of empirical studies, or it may be something closer to primary sources in history, since some areas of these fields depend on direct observation, personal narratives or commentary, as from interviews or case studies.
A secondary source is based on other sources. It includes analysis, criticism, or other intellectual input. Review articles are based on analysis of the published 'literature' (books, articles and dissertations about the topic). Secondary sources can include books, book chapters, articles, especially literature reviews, and some book reviews.
A tertiary source is commonly a resource or tool that helps people find primary or secondary sources. Tertiary sources include most bibliographies, databases and indexes, and library catalogs.
("What's a Primary Source? Information in the Various Disciplines" was created at the University of Arkansas University Libraries. Permission to use this content was given by Necia Parker-Gibson).