Scholarly journals are also sometimes called academic, refereed, or peer reviewed journals, and they're a very important part of college-level research.
The easiest way to understand the definition is with the term “peer reviewed." Many journals send articles to a group of the author’s peers (other experts in their field) to critique, and sometimes even reject, the article before it can be published. Scholarly articles are written BY experts and FOR experts. That doesn't mean non-experts can't read them, but it does mean they sometimes use complicated, technical language. They may be long and occasionally challenging to read if you’re not an expert in your field yet.
Quality control—you still should critically evaluate everything you find, but at least you know other experts have evaluated it too.
Written by experts—journals are where the scholarly conversation takes place and new knowledge is created. As you move forward in your discipline, you may find you're expected to rely on scholarly journals for more of your research.
It’s required—sometimes professors will require you to use scholarly articles, generally because of reasons #1 and #2.
If you're struggling to read a scholarly article, check out these tips for reading journal articles and scientific journal articles.
Time Magazine, Newsweek, Popular Science, etc are usually called "popular sources." Articles are often written by journalists/staff writers and mostly avoid technical language or jargon—they’re written for the non-expert. That doesn’t mean the articles are bad or false, but they’re not original research and they don’t have a peer review process. (Generally, articles in popular sources are reviewed by editors or fact checkers, but not subject matter experts.)
Sometimes, popular sources like magazines and newspapers will be great for your research, and other times you need to show that you're relying on experts to support your arguments by using scholarly articles. Both can be useful, depending on your purposes!
Consult the video "Limiting to Scholarly Articles in Library Databases" (below). It describes how you can make sure your search results come from scholarly journals. The Find Articles page of this guide will point you to more options.