Some conference papers are rewritten for later publication in a scientific or scholarly journal that is peer-reviewed. Some conference papers may be primary literature if they report the results of original research. Popular magazines do not require extensive prior knowledge or special expertise to understand. They often contain colorful pictures and graphics to appeal to a wide range of readers. They are often good sources for information and opinions on topical issues and controversies.
Popular articles are secondary literature because they usually summarize other research.
Scientific or scholarly journals contain reports on the results of research or other scholarly efforts. They often have a serious look with few pictures and illustrations. Articles are well documented with references and bibliographies, and the technical language indicates that the intended audience is familiar with the topic. Many scholarly journals are published by professional organizations. Journals like Scientific American and Science include both scientific and more general articles.