This update was released in August 2013. The purpose of this update was to understand the intent of the user in the query and provide the results best suitable for a user. Instead of ranking a page because of keyword density, this update understands the semantics of query, relevancy of content and provide the suitable results.
For example, if you search for keyword: which is the best business hotel in Hyderabad ? then hummingbird will understand the intent of the user and provide the results for best business hotel in Hyderabad by ignoring the words [which is] and [?] to provide relevant results.