A journal is a periodical publication that contains scholarly information in a subject area. Scholarly or academic journals are collections of journal articles written by professors, researchers, or experts in a given field.
Journals are one type of serial, which is any publication published in parts (usually in regular intervals). Other types of serials are magazines and trade publications. Articles that undergo a review process by other experts before publication are known as peer-reviewed.
Peer-reviewed journal articles go through a checking or verification process before they are published. Other experts in the same field of study as that of the article, examine the article's content to make sure it is valid and correct before the article is published. Articles that have gone through this validation process are known as peer-reviewed articles.
This is a visual image of the peer-review process: