With the amount of information available on the web, finding what you need would be nearly impossible without some help sorting through it. Google ranking systems are designed to do just that: sort through hundreds of billions of webpages in our Search index to find the most relevant, useful results in a fraction of a second, and present them in a way that helps you find what you’re looking for.
These ranking systems are made up of not one, but a whole series of algorithms. To give you the most useful information, Search algorithms look at many factors, including the words of your query, relevance, and usability of pages, the expertise of sources, and your location and settings. The weight applied to each factor varies depending on the nature of your query—for example, the freshness of the content plays a bigger role in answering queries about current news topics than it does about dictionary definitions.
To help ensure Search algorithms meet high standards of relevance and quality, we have a rigorous process that involves both live tests and thousands of trained external Search Quality Raters from around the world. These Quality Raters follow strict guidelines that define our goals for Search algorithms and are publicly available for anyone to see.