The function of a search engine is to match a user’s search query with the best available web page. To do this, it looks at variety of signals that indicate the page’s relevance and authority. These signals (and the degree to which they influence a page) are forever being updated and fine-tuned by search engine companies. They might include, for example, the relevance of the content on a particular page, the number and quality of links pointing to that page, or the quality of the user experience. Search engine optimisation works by using this information to optimise web pages in a way that influences their page rankings positively.