What is HTTP?
HTTP stands for Hypertext Transfer Protocol. It's a standardized format for transferring data between two devices over a network. When you go to a website on your web browser, it uses HTTP get data to and from the website server. That's why all website URLs start with HTTP.
HTTPS Adds Encryption
HTTPS is HTTP with encryption. This is the recommend protocol for all websites today. You can tell that you are access a website via HTTPS either by checking the browser address bar for a padlock icon, or checking that the URL with https://
HTTPS Adds Authentication
In addition to providing encryption between your web browser and the web server, HTTPS also helps authenticate the web server. Authentication means verifying that the web server is who they claimed to be. Just as your bank teller checking your ID before allowing you to access your account, your web browser can use HTTPS to verify that this web server you are accessing is truly from Chase bank, not a hacker masquerading as Chase.
Selecting the right protocol in your URL
A website can technically choose to support only HTTP, only HTTPS, or both. But most websites these days only support HTTPS. For example, if you go to http://www.google.com, it will automatically switch (redirect) to https://www.google.com.
When setting up your website for scanning, if your website supports HTTPS (the most common and recommended method), choose HTTPS in the "Website Protocol" dropdown. If your website only supports HTTP, you should select HTTP instead (and you should also consider switching to HTTPS as soon as possible).
Not sure what your website supports?
Enter your website into a web browser with HTTP, and see if the browser is automatically redirected to HTTPS (with a padlock icon). For example, in a browser, go to http://zeguro.com and see if it redirects you to https://zeguro.com (yes we do, of course).