Professional literature is peer-reviewed. Articles in professional journals are written for and reviewed by people in the profession--researchers, clinicians or academics.
Many professional articles are very technical. Be sure you can understand an articles before choosing to work with it. A good way to find out if you are interetsed in the subject matter of the articles is to read the abstract or summary.
Many professional and peer reviewed journals publish book reviews. Book reviews are usually not appropriate as sources for your research on a topic--you need to read the whole book! Usually "Review" or Book Review" will appear somewhere in the database citation. In most databases you can limit the search to exclude book reviews.
