Peer-Review is the process that journal editors use to ensure that the articles they publish meet the standards of good scholarship.

Academic papers, journal articles, and research papers are examined by a panel of other scholar in the field. The panel may decide to accept the paper, recommend revision, or reject it completetly. 

Note - while not a perfect process, it can be presumed that any resource that passes the peer-review process can be considered to have the highest level of academic credibility. Despite this, it is still crucial to consider other elements such as currency and authority when evaluating a source. Not all journals use the same peer review process and not all seemingly academic journals are peer reviewed. Some lecturers may specify that only peer-reviewed resources are to be used in assignments.

Some databases allow you to narrow your search to return only peer-reviewed results.  This process differs from database to database and is often as easy as ticking a box that says 'peer-reviewed'.

You can verify the peer-review status of a print journal issue by checking for information about the editorial board at the front of the journal.  Information about print and e-journals is also available from Ulrichsweb global serials directory or from the journal's website.