Popular articles are the ones you run into everywhere on the internet: CNN, ESPN, HuffPost, Refinery29, BonAppetit. They're written to inform readers on a topic. They're meant to be read front to back, with the most important information towards the front of the article, after the interesting opening written to catch a reader's eye. Written by journalists, these are written for people interested in the topic, but who probably don't have an academic interest or degree in it, i.e. the general public. They contain stories, facts, opinions, people, and dates.
Scholarly articles aren't ones you find everywhere. You won't recognize the names most of the journals they come from yet. They're written to educate readers. Because scholarly articles are longer and more involved, they usually have an organizational structure. Figure it out and you've got a roadmap to the article. Even before the sections of the article, start with the abstract, usually a paragraph set apart from the rest of the article at the beginning. Also, because scholarly articles build on previous research and scholarly conversations, you will see a section explaining how this is new and different and builds on previous stuff. Don't get bogged down in that section (the literature review, usually unlabled, but full of citations); come back to it once you have a handle on what's happening in the article. These articles are written by scholars, academic experts in the field they're writing about, for scholars, other experts, academics, and students. They assume you have basic knowledge of the subject area and sometimes even specialized knowledge so don't be afraid to look up words and terms you don't know. They contain experiments, theories, results, and answers to research questions.