Primary research articles (also called empirical/clinical studies or research articles) contain firsthand information or original data on a topic that is not interpreted, evaluated, or analyzed. These articles also include components or a variation of these components: Introduction, Methods, Results, and Discussion (known as the IMRaD format). Primary research articles are usually peer-reviewed (i.e. article was critically evaluated evaluated by experts in the field before accepted for publication).
Primary Literature (sometimes called primary research articles, original research article, primary sources)
Secondary Articles (sometimes called secondary sources)