The most recent search improvement in Google is called Google Instant. It displays to you the results as you’re typing. Its main goal is to assist the searcher obtain faster and better results. The main concept of this came from the fact which usually type slowly but reads rapidly: usually takes 300 milliseconds in between keystrokes, however, just 30 milliseconds for a quick look to other portions of the page. Therefore, this indicates that it would be more helpful to scan the results page as you’re typing.
Google Instant: How to Enable or Disable this Latest Improvement in Google Search?