Wikipedia is a free online encyclopedia that anyone can edit and contribute to. While articles are monitored for accuracy and cite reliable sources, not all entries can be thoroughly reviewed before publication. When using Wikipedia, users should evaluate articles using the "5 W's" - who wrote it, what information it provides, where it comes from, when it was published and last updated, and why it should be used - to help ensure reliability. The key is to verify all information on Wikipedia through other sources.