This is not always an easy answer because:
peer reviewed journals have non-peer reviewed content in them.
First check if article is scholarly. Check if it has:
Is the article Peer reviewed?
Peer reviewed articles are a special kind of scholarly.
To make sure you have to check if the journal says that it is peer reviewed
To do so:
Search for the journal title in Urichsweb. The term they use for peer-reviewed is 'referred'.
You can also:
Again, not everything in a peer reviewed journal is a peer reviewed article.
As you professor or a librarian if you are unsure.