It contains the advice or opinions of one or more Wikipedia contributors. This page is not an encyclopedia article, nor is it one of Wikipedia's policies or guidelines, as it has not been thoroughly vetted by the community. Some essays represent widespread norms; others only represent minority viewpoints.
This essay relates to ways to find reliable sources, depending on the particular topic (see below: List of suggested sources). There are the general Wikipedia policies:
However, editors new to a particular topic might not realize some specific major publications are preferred as sources. Guideline WP:MEDRS suggests sources for medical text, but other subjects need recommendations for reliable sources, as well.
The term "reliable" is a relative measure, depending on context. The answer to the question, "Is X a reliable source?" should always be "For what?" because expert publications might be better sources to back rare details, whereas news reports cover general aspects. For example, a top newspaper is typically unable to match the expertise of a medical journal or computer-technology magazine, but news reports are the most likely to have recent information, for major facts (but not for precise technical details, which are sometimes mistaken in general news reports).
The above-mentioned list is just a small list of suggestions, but it provides a specific starting point for editors unfamiliar with the major sources covering each specific field.
^Note that not all sections of The Guardian, or of any "reliable" newspaper, should be considered reliable sources for purposes of establishing notability-- The Guardian's "Review Anything" section has been found to be an inadequate source for establishing real world notability in at least one deletion discussion.