Journal articles that are peer-reviewed have been critiqued by other experts before publication.
To determine if an article is peer-reviewed or not, you need to check if the journal in which the article was published is peer-reviewed. You can do this by using the database Ulrich's web. For instance, in the following citation:
Barthlott, W, Wiersch, S, Čolić, Z, & Koch, K 2009, 'Classification of trichome types within species of the water fern Salvinia, and ontogeny of the egg-beater trichomes', Botany, 87, 9, pp. 830-836.
Botany is the journal title. Using Ulrich's web, type in the name of the journal, in this case Botany. (Do NOT enter the title of the article.) If the journal is listed as "refereed" (another word for peer-reviewed), your article is in a peer-reviewed journal. Therefore, most articles in this journal will be peer-reviewed. Exceptions to peer-reviewed articles in a peer-reviewed journal include news items, commentaries, and letters to the editor.
In some databases, such as Academic Search Complete , you can click on the name of the journal and the database will list information about the journal, including if the journal is peer-reviewed or not. Other databases allow you to limit to see only results that are peer-reviewed. To determine if you can limit to peer-reviewed journals, look in the database's help section.