All scholarly sources are good; not all good sources are scholarly.
A New York Times article or government statistics are (probably) great, wonderful, reliable sources, full of credibility and accuracy and just the kinds of information you should trust.
They are not, however, "scholarly."
Scholarly is a very specific type of good, credible, reliable information source.
Scholarly sources are written by formally trained and educated experts in a field. They tend to provide an in-depth look at a very specific topic (as opposed to an overview or summary) and always have lots of sources cited to back them up. They are published by professional or academic organizations.
Some even go through a peer-review process before publication, through which other experts critically evaluate the content and evidence of an article.
The Three Rs
Is your source
Recent? Reliable? Relevant?
Is this source up-to-date? Is it about my topic, and does it go into enough depth? Does it come from an authoritative source? Is the information accurate (and are there citations given to back it up)? And why was this information written in the first place?
Research Companion has a Source Evaluation Aid tool to help you determine important information about websites, periodicals, and books like who publishes them or if they're a known bad actor.