In order to give searchers more accurate results Google may reform queries based on co-occurrence in search sessions. By using co-occurring searches performed by other users Google may create a seemingly more intuitive environment that can yield better quality results for you!
Let’s say you are looking for a recipe, so you type in the keywords “worlds best pizza”; your search is going to result in restaurant reviews and local ads. But, with the new reforms if searchers often go back and search for “best pizza recipe”, that co-occurrence will effect your results as well. This could be a great tool for allowing users to narrow general search topics to more quickly find what they are looking for!