The Google team responsible for search, recently announced an update to the engine behind the beast. This is the biggest update they've made in 12 years. They call this latest update hummingbird. Here's some details if you want to read more.
We're still waiting to hear all the details about it, but from what I know, it's geared to analyze searches and return answers to questions versus just looking at keywords independently. I have a droid phone and notice now a woman like siri responds to my questions when I use the voice search. She tends to keeps me company when the sox are playing and I'm on the road.