Your website will be able to use secure, encrypted HTTPS connections with your visitors.
This ensures the safety of any sensitive data passing between your visitors / customers & your website.
In addition, it has been acknowledged by Google, that having a secure HTTPS SSL website brings some benefits to Search Engine Optimisation (SEO) marketing.
Finally, web browsers like Google Chrome, will actively display a warning message to a user if a website doesn't use a secure HTTPS SSL connection, thus giving a very negative user experience & lowering visitor confidence in your website.