Google announced last year that they would eventually start notifying website visitors that the sites they were visiting are not secured with an encrypted SSL connection. You can tell when a site is secured because you will see a padlock icon (and the word "Secure" in Chrome) next to the URL, as well as seeing "https" included at the beginning the URL including, instead of "http".
So what does all this mean to you, as a casual internet user?
According to Google, "When you load a website over HTTP, someone else on the network can look at or modify the site before it gets to you." This means that someone could present a fake page and try to present false information to you, or gather the data you're submitting to a site. If you're entering or sending any data through a website, especially financial or personal data, like your name, address, or credit card information, make sure the site is marked as Secure before submitting.
So what can you do, as a casual internet user?
You can install an extension like HTTPS Everywhere that will encrypt your browsing and provide more security. And you can notify website owners when their sites aren't secure.
If you have a website that isn't secure, the good news is that it's easier and cheaper than ever before to implement security measures like SSL certificates. Services like Let's Encrypt even offer free SSLs, and hosting providers like Cloudways and Bluehost provide quick and easy integration for many websites they host.