Search History was launched in April 2005 and grew from web search to image search (July 2005), news (November 2005), Froogle (February 2006), Google Video (June 2006) and the music you listen (August 2006). Search History is automatically enabled if you activate Google's Personalized Search and can be accessed by clicking on "Search History", next to your Google username.
You can think at Search History as a persistent memory that can help you search over your past searches.
