A cache is an essential component of a web server. With applications like Magento, cache plays an essential role in application performance because it drastically reduces the load on the application and speeds up page response. As a result, the user experience improves significantly.
Faster website is better for the SEO of the website and performs well in the Google SERP.
Click the below mentioned link to know more about Magento Varnish Cache Configuration.
https://www.cloudways.com/blog/magento-2-varnish-configuration/