Another high quality explanation from Common Craft:

“Wikipedia is an amazing resource, but it’s not always clear what helps to ensure that the articles are factual and high quality. This video discusses wiki technology and the policies that make Wikipedia work. We worked with the Wikimedia Foundation to ensure that it reflects Wikipedia’s values and practices. It teaches:

Why an online encyclopedia is needed
The basics of editing a wiki website
How volunteers work to ensure quality
The two big rules that govern every article”

Link to the video page.