Scholarly journals require that all articles being considered for publication be reviewed by one or more of the authors peers (specialists working in the same field). If the reviewers indicate that the article is accurate, up-to-date, well-reasoned and otherwise acceptable, the journal will probably publish it. If they recommend rejection, it will probably not be published.
A third option is called revise and resubmit, which means that the reviewers think the article has promise but that it needs additional work before it is ready for publication. They suggest changes the author should make, after which she or he can resubmit the article for reconsideration.
One way is to use the database you are searching in. Some databases allow you to check a box for peer-reviewed or scholarly sources. Also if you click on the publication title it will take you to a page of information about that publication; depending on the database it may tell you if it is peer-reviewed.
Another way is to use a directory such as Ulrich’s Periodical Directory. This is a database of periodicals with detailed records on thousands of newspapers, magazines, newsletters, scholarly journals, collections, and other materials. It does not include articles from those publications, just information about the periodicals themselves, including whether they are peer-reviewed or not. (Ulrich’s uses the term refereed.) As of May 2011, people with a King County Library System (KCLS) card could access Ulrich’s through the KCLS databases.
Some databases allow you to limit your search to scholarly or peer-reviewed journals. However, they are not always accurate! Some periodicals that are not scholarly do slip through the cracks, so dont rely on the databases alone to determine whether the source is a scholarly one. There is no substitute for the checklist to determine whether you have a scholarly source.
(See the next question as well.)
Not necessarily. For one thing, not all peer-reviewed journals are scholarly journals. For example, the Columbia Journalism Review is a trade magazine for journalists. It is peer-reviewed, but it is not a scholarly journal.
For another thing, just because it appears in a scholarly journal, that does not mean that the article itself can be considered a scholarly source. It hasnt necessarily even been peer-reviewed. Editorials and book reviews, for example, are frequently published in scholarly journals but, unlike full-length articles, they are not peer-reviewed. They are also typically not in-depth enough to be considered scholarly in the strict sense of the word. Therefore, simply because you found something in a peer-reviewed journal doesnt mean its a scholarly source. Again, there is no substitute for the checklist.