Basic Research Definitions
Your professors will often use the words "scholarly" and "academic" synonymously when describing sources you need to collect for a research paper. These sources are typically written by and for professional researchers like your professors. Sometimes students help write and publish these too, but most often students use them to complete coursework.
Original research, primary research, or just "research" articles refer to articles that include details and the conclusions of a new experiment or study. They often begin with a brief literature review which is a summary of research that has already been published on the topic. The authors of the article completed the experiment or research study. Experts often expect these articles to be peer reviewed. To identify this kind of article, look for a "methods" or "methodology" section.
Authors of secondary research summarize, analyze, and draw new conclusions about others' original/primary research. Many research papers you write during your first and second years of college would be considered secondary research.
A literature review article is an example of secondary research. These articles only summarize others' primary/original research. The authors of this kind of article will not write about a new experiment or study.
If you are unsure about whether or not a source is acceptable, be sure to ask your professor.