A journal, sometimes called a periodical or serial, is a specialist publication containing detailed research, analysis, new ideas or theoretical discussion on a specific topic.
Journals are published in regular issues (weekly, fortnightly, monthly, quarterly, annually etc.), each of which usually has a number.
Each issue contains articles by different authors.
Journal articles do not take as long to produce as books, so generally contain more up-to-date information.
Articles in academic journals are peer-reviewed (scrutinised by other academics before publication), ensuring their quality and reliability (although you may disagree with the views expressed).
Electronic journals (e-journals) are usually electronic versions of printed journals, although they may contain additional articles or more up-to-date content. Occasionally e-journals exist where there is no printed version. E-journals have the advantage that you don't always have to go to the library to access them, and you can download or print articles, within copyright limits. For some journals, however, particularly older issues, you will still need to use the printed version. Many journals are available online, via UCL Library's subscriptions.