Google uses HTML tags to understand the content structure and hierarchy of a web page. This information helps Google better understand the relevance and context of a web page's content, which can in turn improve its ranking in search results. Some commonly used HTML tags that help with search engine optimization (SEO) include header tags (H1, H2, H3, etc.), title tags, meta description tags, and alt tags for images. These tags provide information about the page's title, description, headings, and images, which can help Google understand the context and purpose of the page, and display relevant information in search results.