Launched in October 2015, RankBrain works in major part with the Hummingbird algorithm to further help Google understand the meaning behind queries and provide more relevant results.
It is the only Artificial Intelligence (AI) used in Google search results and relies heavily on machine learning. According to Google, it is their third most important ranking factor.
The RankBrain algorithm was online from April 2015, however, it wasn’t introduced to the world until October when Google explained RankBrain and its purpose to better handle queries that have not been searched before.
Around 15% of queries processed by Google are new and unknown so there had been a growing need to find a suitable method for processing such queries and organising the results. There are many ways to ask even the simplest of questions and RankBrain may be required even more as voice devices become increasingly popular.
The algorithm uses AI to convert large amounts of written language into mathematical figures or equations that the computer can make sense of. If RankBrain does not recognise a word or phrase then the machine can make an informed guess as to what language may have a similar meaning and therefore adapt the results to give users the best possible responses to their query.
It is important to note that the RankBrain algorithm update only used to impact a small number of queries but is now involved in almost all queries searched on Google. However, it’s influence will only be minor for searches recognised by Google as it only comes into real action when Google is unsure what a query means.
As it is not a Natural Language Processor (NLP), RankBrain cannot consider and infer what you meant in your search based solely on the language used. Instead, the Update uses several databases based on entities such as people and places as well as vectors to determine relationships between similar queries and provide informed results.
In terms of SEO best practice, it is possible to optimise your content for RankBrain by writing naturally. Conversational and humanised language is favoured by the algorithm although aside from this there is little you can do as time would be better spent optimising other elements of your website. The reason for this is that the results generated by RankBrain are designed to change and retrieve better results, so optimising for it would prove to be unnecessary as the change is too constant and often very few people are searching for that query anyway, hence the need for RankBrain.