Google has introduced a new algorithm, codenamed Hummingbird, for the first time in three years. It improves the way the search engine interprets your requests. It has been up and running for a month already and has affected 90 percent of Google searches.
The new algorithm is said to be particularly useful for longer, more complex inquiries and provides a more natural interaction with the search engine. The answers to your questions this time are based more on an intelligent understanding of your searches than an indexing of websites done by the previous algorithm Caffeine. Hummingbird understands the relationship and concepts of words rather than just taking these words at face value.
Source: BBC