Google uses algorithms to determine the significance of webpages and provide relevant search results. The main Google algorithms include Panda, Penguin, Hummingbird, mobile friendly update, Possum, and Pigeon. Panda assigns quality scores to penalize low-quality content while Penguin aims to downrank manipulative links. Hummingbird helps Google better understand search queries. The mobile friendly update prioritizes mobile-optimized pages and the Pigeon update incorporates traditional SEO factors into local rankings.