Article sources are generally categorized as a popular, trade, or scholarly publication. Your professor may require that you use scholarly articles for your assignments.
Popular publications, for example magazines and newspapers, are written by paid journalists for the general public. The articles often provide general information (who, what, when, and where) about a current news event or topic.
Trade publications include articles focused on a specific profession or industry. The articles are usually written by experts in the field to inform readers about current trends and practices.
Scholarly publications are sometimes identified as academic, peer-reviewed or refereed sources. The authors are experts in their field and are writing for other experts and students of that field. These journals utilize a peer-review process to determine the accuracy and validity of the work and its contribution to or advancement of knowledge in the field. The articles in these publications range from original research to review articles (systematic review, meta-analysis or literature review). These publications may also include editorials, opinion pieces, and "news items" which do not go through the same rigorous review process.
Many library databases provide options for filtering or limiting your search to specific types of publications. You always want to evaluate your results.