SSL stands for Secure Sockets Layer, a security protocol that is used to secure the session between a browser and a server. Transport Layer Security (TLS) is the protocol that is actually implemented today. To keep things simple, however, this encryption is still commonly referred to as SSL.
No matter which way you say it, SSL or TLS, we're talking about the cryptographic protocol that encrypts any information input into a website. That way, if someone is trying to eavesdrop, they can't see what is exchanged between your website and the server receiving your visitor's data.
When a website does not use SSL, the domain has 'HTTP' before the name, e.g., http://example.com, and the traffic between the browser and server is sent using the HTTP protocol. The problem with unsecured websites is that most browsers today indicate that a site is not secure. Information that is input on that site is sent to the server in plain text. So, if someone wanted to gather login credentials for visitors to your website, this would make it very easy for them to do so.
In contrast, if you utilize an SSL, your data is encrypted before being sent, and your site displays HTTPS before the domain name. With your website's traffic secured, whenever visitors input any information, such as login credentials or credit card numbers, no one can intercept that information. When visitors are on your site, they'll see a padlock next to your domain. This padlock indicates that your site, and in turn, the data they share on your website, is secure from prying eyes.
While we provide our customers with access to webmail with our hosting accounts, most people use a third-party email client on their phone or computer to check and send emails. You'll notice when you're following the steps to manually add your email to any desktop client or mobile device that it asks for information to connect to the server where your email is hosted.
Outside of asking for your credentials and whether or not you want to use IMAP or POP3 when setting up your email client, it will also give you the option of using SSL/TLS. Opting in to use SSL works the same way when visitors are on your site. When you're signed into your email online, that data is encrypted between your email client and the server. Without using the SSL/TLS option, that information is sent in plain text, which puts it at risk of having someone eavesdrop on it.