Google Official Actionable SEO Wikipedia

Hi guys

I am dedicating this thread to all Official videos, Twitter posts and recorded information that has mentioned how Google actually works.

Note: Please only post info that are recorded facts from Google official sources, also mention the exact source.

Starting with:
Matt Cutts 2010, topic: How Search Works.
Simply search "How Search works" on Youtube and choose the video made by Google official channel

Valuable sentences:
1-They index pages based on their links from other sites
2-Pages are chosen based on more than 200 questions, like:
a-How many times does this page contain this keyword,
b-Do the words appear on the Title, on the URL, directly adjacet, does the page include synonyms for those words
c-Is this page from "quality" website, or is it low quality? even spammy?
d-What is this pages PageRank: Rating a page's importance by looking at how "many" outside links point to it, how how "importnant" those links are
3-Search result includes a Link, a Title and a Snippet of Text to help decide if this page is what you are looking for (Opinion: CTR defines a correct search match)

Link: Google developers blog, topic: best practices for running multiple sites

Useful sentences:
1-What makes your sites unique and compelling enough to make users want to revisit them, link to them or even recommend them to their friends?

2- If you registered several domains but only want to focus on one topic, we recommend you create unique and compelling content on each domain or simply 301 redirect all users to your preferred domain.