Ever since Google notified the Web world about its move to RankBrain, question after question has been asked about how it works and what, precisely, it will impact. Let's try and clear up at least a little of the confusion.
RankBrain is essentially a method used by Google to understand more (through artificial intelligence) about the queries it receives. Often, the search terms and phrases entered by end-users are quite ambiguous (there are even search queries that Google hasn't ever seen before if you can believe it) and it can be difficult to understand what the user really, actually wants.
The introduction of RankBrain however, which is now used on a large percentage of search queries the engine sees each day, aims to correct that rather significant problem by using artificial intelligence to well, guess what searchers mean - just like a human might do.
What does this mean for your search engine optimization campaigns?
Know that RankBrain doesn't necessarily add any new ranking signals but, depending on the query, it may weigh the existing signals differently (so it won't impact crawling or indexing).
As always, if you're focused on providing content to users that fulfills their information, education or entertainment needs, not much needs to be done really.