The searcher first sees a few results for specifically what they've entered. Then, the searcher is asked if they're "dissatisfied" with what the results they're seeing. Without needing to click, a suggestion is made and a new result(s) is listed. I'm thinking of it of variation on a traditional spellcheck.
Btw, I tried transposing letters of acronyms and also misspelling words and was unable to find a "dissatisfied" option but I rarely seem to be able to see Google UI test on my home computer.
Postscript: Google has confirmed this UI test.