Peer-review refers to the process an article goes through before being
published. It is reviewed and evaluated by other scholars in the field (peers)
for accuracy and to ensure it contributes to the field. Some peer-reviewed
journals reject more articles than they accept.
I found an article written by a scholar. Is it scholarly?  
Not necessarily.  Scholars sometimes also write for non-scholarly trade
journals and magazines so it is important to think about whether the
publication is a scholarly journal, trade journal or magazine, as well as
who wrote the article.
Are all articles in scholarly journals peer-reviewed?
Many, but not all scholarly articles are peer-reviewed and some journals
contain a mix of both peer-reviewed and non-peer reviewed articles. Book
reviews are one example of scholarly articles that are not peer-reviewed.