RankBrain is a machine learning system that Google developed. It was designed to help Google understand how the search engine should rank pages. RankBrain is the third most important factor in ranking a page after links and content.
RankBrain has been used since October 2015, but it was only publicly announced in 2016. RankBrain is an artificial intelligence algorithm that helps Google understand what users are searching for and what webpages are about, allowing it to rank webpages better.