Before you look for articles, you should determine what your topic is and identify keywords and phrases.
State your topic as a question: How does social presence theory affect online learning?
Once you have identified keywords and phrases and synonyms, you are ready to formulate searches.
For example, for the topic How does social presence theory affect online learning? you might search for:
"social presence theory" AND "online learning"
If you don't find anything with that search, then you may want to think of adding some synonyms to your search:
("social presence theory" OR SPT) AND ("online education" OR elearning)
What is a popular magazine?
Sources published in newspapers and magazines intended for general audience. You will not find references. The author may write about politics one week and education the next.
What is a trade publication?
What is a scholarly journal?
Also called an academic journal. It is a periodical written by academic experts in that specific field. The articles submitted are reviewed by experts in the same discipline to determine if the article should be published. Articles are academic in nature and often research-based.