This core update from Google is intended to further improve the quality of search results. Users should find content that is helpful instead of content that is merely intended to generate clicks. The core update itself is more complex than other previous updates and will take up to a month to complete. This is because several different systems will now be used to determine the usefulness of content for the user. Such an approach based on a variety of indicators is already used to determine reliable information.By switching the analysis of usefulness from one indicator to several systems, there may be greater changes in the ranking. Authors do not need to change anything in their writing if they are already creating content that meets the needs of readers. Useful, reliable and reader-focused content will therefore continue to perform best.You can find more information about Google's Core Update on their FAQ page.