1. What does peer reviewed actually mean?Peer review is a particular type of quality control, frequently used in academic journals. When a researcher submits an article to a journal, they expect that it will be reviewed for quality by other researchers working in the same discipline, field, or sub-field.  
2. Does "peer-reviewed" article mean the same as "scholarly article"?

Technically, no. There are a lot of sources that are written by and for scholars that have not gone through peer review.  "Scholarly" is a broader term than "peer reviewed."  

However, many instructors use these terms interchangably. If you are concerned, you should ask your professor if they would like you to use peer-reviewed sources, or if they are okay with a broader range of scholarly sources.

3. Does "peer reviewed" mean the same as "refereed"?Yes, peer reviewers are sometimes called "referees."
4. Who writes peer-reviewed articles?Most peer-reviewed articles are written by researchers.  This is a broad term that includes people working in the lab, in the field, in the classroom, in the library, in archives and more.  Many of these researchers are employed by colleges and universities, but not all.  You will also see papers reporting on research done by businesses, government agencies, think tanks, hospitals, labs, research centers and more.
5. Who reads peer-reviewed articles?Students like you read a lot of peer-reviewed articles!  But students are usually not the intended audience.  Most peer-reviewed articles are written for researchers and experts.
6. What are peer-reviewed articles about?Peer-reviewed articles can be about many things, but most of them are about research projects. Scholars and experts do research, and then write articles where they report on the results of their studies.  Most peer-reviewed articles are therefore fairly focused on the results of a specific study or experiment.
7. Do all peer-reviewed articles have the same format?No. Every discipline has its own set of standards and practices for communicating research. Many articles in the sciences and social sciences do share a common format, but that does not mean all peer-reviewed articles look the same.