SSL Certificates provide the highest level of security to your website.
Secure Sockets Layer (SSL) is a standard security technology for establishing an encrypted link between a server and a client - typically a web server (website) and a browser, or a mail server and a mail client.
This is important because the information you send on the Internet is passed from computer to computer to get to the destination server. Any computer in between you and the server can see your credit card numbers, usernames and passwords, and other sensitive information if it is not encrypted with an SSL certificate.
If your website doesn't collect sensitive data, like credit cards or social security numbers, you may not have needed an SSL certificate in the past. However, with the new browser notices, it's now important to ensure every website has an SSL certificate and is loaded via HTTPS.