SSL is a cryptographic protocol that was created to keep communications over the Internet secure. More and more website administrators have replaced the http protocol with https to get a series of advantages:
Encryption of information – to block the interception of sensitive information entered on a website, such as user, passwords, or personal data.
A website might seem reliable, but how do you know for sure? Domain Validation checks the domain name of a website to make sure it's not a fake site created for phishing or scams. Organization Validation checks the credentials of a certificate organization, and Extended Validation is a more stringent verification process with a green bar across the top of your screen.
Google and other search engines rank websites higher for their use of the https protocol. This means that your website ranks better, and you gain more qualified traffic.
When browsing a website, you can easily identify the certificate type by looking at the green padlock in your browser toolbar. Websites with EV certificates (which offer maximum security) are displayed with a well-known "green bar".