You complete me by Alexander Reelsen.
From the post:
Effective search is not just about returning relevant results when a user types in a search phrase, it’s also about helping your user to choose the best search phrases. Elasticsearch already has did-you-mean functionality which can correct the user’s spelling after they have searched. Now, we are adding the completion suggester which can make suggestions while-you-type. Giving the user the right search phrase before they have issued their first search makes for happier users and reduced load on your servers.
In the context of search you can suggest search phrases. (Alexander’s post is a bit dated so see: the Elasticsearch documentation as well.)
How much further can you go with suggestions? Search syntax?