New Dangers of Secondhand Smoke
This Time Magazine article about secondhand smoke is a good example of a popular source. You can easily find articles like this via a Google search, while scholarly sources are more easily accessed through library databases (or Google Scholar).
Like most popular sources, this article is a good bit shorter than the average scholarly article. Unlike a scholarly source, the author's credentials are not clearly listed. While scholars sometimes write popular sources, the author of a popular source is often not affiliated with a university.
Although there are no ads in this article, you will often find advertisements in a popular source, and you are also more likely to have pictures included.
Finally, there is no abstract, no methods or discussion section, and a list of references are not included.