Google's Hummingbird update was a major rewrite of its search algorithm focused on understanding search queries through entities and relationships rather than just keywords. This has implications for e-commerce sites, which should optimize to be recognized as entities, build relationships between products and categories, and focus on answering queries through in-depth content rather than just keywords. They also need to optimize for voice and mobile search through measures like prioritizing local search results and ensuring their content is accessible across devices.