Relevance denotes how well a search result satisfies the user information need. In addition to the search engine components (i.e., indexer and query parser), there are many other components that impact relevance. e.g., user understanding , data optimization, domain knowledge, etc. Improving relevance remains the main and most challenging goal of each search engine. Indeed, relevance can be subjective, therefore hard to measure and to improve. In this talk, Saïd will demystify the concept of relevance by defining its main components. For each component, he will present the technology enablers, the data, and processes that are required in order to measure and improve relevance. In this talk, attendees will learn how to provide a relevant user experience and track it over time.