Apparently the way it works can be described by the way we read. New readers (children) read and see character by character, and eventually syllables. Advanced readers just recognise words like they would a photo. So when you look at the word "Chess", you just see "Chess" as a picture that you recognise without having to read it. Speed readers can see entire sentences or even the following sentence in their heads before reading it out.

Those chess moves are easy for the grandmasters to visualise as they're just words or sentences to them, so they can just see them without having to think much about it.

I saw the analogy in a book I was reading about the brain and cognitive ability. Interesting stuff.