Query suggestions are phrases that you want the search system to suggest to users as they start typing a query. For example, as you start to type "Chicago", they may be able to pick a word that starts with "Chicago" from a list below the Search Box.
The Query Suggestion feature needs to be enabled at the Service Application level to be activated.Once this is done there are 2 ways to implement query suggestion.
1. Manually upload the query suggestion list into SharePoint.
2. The search system automatically creates suggestions for a query when users have clicked one or more of the results for that query at least six times.
Manually uploading the query suggestion
1. Browse to Central Administration -> Service Applications -> Search Service Application.
2. Go to Queries and Results -> Query Suggestions
3. Select Show Query Suggestions
4. In Always suggest phrases -> Import from text file
5. Browse to Central Administration -> Monitoring -> Review job definitions ->Prepare query suggestions -> Run Now
