Hummingbird allows the Google search engine to better do its job through an improvement in semantic search. As conversational search becomes the norm, Hummingbird lends understanding to the intent and contextual meaning of terms used in a query.
It seems that with Hummingbird, Google can now better answer those longer-tail queries even if a page is not optimized for them. So some pages may have a better chance of being found for certain queries now.
See online : Google Introduced Hummingbird