Search Query Refinement Suggestions
Query refinements are now offered by all the three most popular search engines.
The goal of these links is to let users search with a more specific and possibly more relevant query that will satisfy their intent.
In March 2009, Google has started giving this service of refinements by implementing Orion Technology, which was acquired by Google in 2006.
The goal of this enhancement is to provide a wider array of refinement choices.
For example, a search on principles of physics will display refinements for the Big Bang, angular momentum, quantum physics, and special relativity.