RankBrain is not another name for someone skilled at SEO, though perhaps it should be. It is the name of the machine-learning artificial intelligence technology Google uses to help deliver the right search result, even when the right search result does not contain any or much of the original search query. That covers the “what is it…” but what is it for and what does it do? RankBrain is intended to “learn” how people search on Google. Google then uses that information and applies it to the Hummingbird search algorithm to determine the relevancy of pages to a given keyword or keyword phrase. To actually learn, then, means to adapt to search concepts, language, and patterns or connections without requiring additional human programming or input.