RankBrain is a tool used to understand a web user’s intent when they key in certain search terms or queries. It’s a system built using machine learning and artificial intelligence, helping a search engine understand what a user wants to see from any query or text they type into a browser window.
Because RankBrain uses artificial intelligence, it’s able to make informed predictions on terms it’s never seen before or words it’s never been exposed to. It does this by referring to its huge catalogue of learned phrases and words and analysing historical searches that may be similar to the one keyed in.