PageRank allows Google to quickly scan its index and produce highly relevant results to a search query, often in less than half a second *
Google looks to see how many links a page has from other pages on the web
Each page receives a score based on how many links there are to it, as well as the relevance of each site of which has a link to this page
Important, high-quality sites receive a higher PageRank, which Google remembers each time it conducts a search *
This technique is fully automated, with no human intervention to determine the value of a page's importance