Graph Search builds on the newsfeed and timeline, which are already part of Facebook accounts, to amalgamate information within the search function which is interesting to you; such as all the photos you have ever liked, or which restaurants your friends have been to nearby.
What does this do for users?
If 2 people do a google search for ‘apple’ both are going to get (almost) the same results. In their promo video Facebook say that the potential depth of personalisation with Graph Search is much, much greater. New questions can be asked, which are more subtle, nuanced.
‘Facebook used to be about communicating with people you know in the real world, now it is also about finding and connecting with people you should know. This will make the world feel a bit smaller.’
Graph Search is currenty only available currently in the US, but you can go on the waiting list.
Further information can be found here.
You can see the official Facebook videos here.