The change builds on top of its previous �Caffeine� update in order to deliver more up-to-date and relevant search results, specifically those in areas where freshness matters. This includes things like recent events, hot topics, current reviews and breaking news items.
Google says that the new algorithm knows that different types of searches have different freshness needs, and weighs them accordingly. For example, a search for a favorite recipe posted a few years ago may still be popular enough to rank highly, but searches for an unfolding news story or the latest review of the iPhone 4S should bring the newer, fresher content first, followed by older results.