Popular periodical articles are written by journalists for the general public. Popular magazines typically have many colorful illustrations and advertisements but not bibliographies. Popular magazines are usually published weekly or monthly.
Scholarly articles are written by academic experts for academic readers. Scholarly journals typically have bibliographies but few if any colorful illustrations and advertisements. Scholarly journals are usually published about four times per year. Most scholarly journals are peer-reviewed. Peer-reviewed or refereed articles go through a process whereby experts in a field recommend whether to publish the submitted results of original research or not.
A number of periodical databases, including the ProQuest and EBSCO databases, sort the search results into popular, scholarly, and other categories. In these databases, It is the periodical, not the individual article, that is being categorized.