Wikipedia:Training/core/Verifiability
Beyond the five pillars, there are a few more important guidelines to keep in mind. First:
Verifiability
Since Wikipedia is the online encyclopedia that anyone can edit, for content to remain in Wikipedia it must be verifiable, which means that people reading and editing the encyclopedia can check that information comes from a reliable source.
This video explains the importance of "Neutral Point of View" and "Verifiability" and how they work on Wikipedia.