Unlike the previous Panda and Penguin updates which were initially released as add-ons to Google’s existing algorithm, Hummingbird has been cited as a complete overhaul of the core algorithm. While it’s believed that many preexisting components of the core algorithm remained intact, Hummingbird signaled Google’s commitment to an increasingly sophisticated understanding of the intent of searchers’ queries with the goal of matching them to more relevant results.
Google announced Hummingbird on September 26, 2013, but it had actually already been in place about a month prior. Whereas previous algorithm updates like Panda and Penguin sparked significant reporting of lost traffic and rankings, Hummingbird did not appear to have drastic negative impacts on the general web. It was largely understood as having a positive influence on the accuracy of Google’s knowledge base known as the “knowledge graph.” However, the local SEO community theorized that documented effects had been felt in the local search engine results.
Source: Moz
