Scholarly journals are where the experts talk to each other. This is where the newest research and ideas are first published. Sometimes in some fields, researchers develop ideas from journal articles into books. If you cannot understand these articles, read encyclopedia articles for background in the field. Instructors frequently require scholarly, peer-reviewed articles. Peer review is when another expert in the field reads the article before it is published in order to confirm that the methods used in the article conform to the requirements of the field.
Most of these databases include non-scholarly material. Look for the Scholarly or Peer-review button and check it.