HTTPS, or HTTP Secure, or Hypertext Transfer Protocol Secure, is a combination of HTTP and SSL, which stands for Secure Sockets Layer. I know it's bad form to define a word with its root, so in Old People Language, HTTPS is what you see in your address bar when you're using a secure connection.
Like logging in to your LinkedIn account:
Or your LinkedIn account:
Or anything you'd consider secure, really. Now, this tip isn't foolproof, but when I'm worried about something I'm logging in to, I check for the s in my address bar. HTTPS does have its limitations, so it's not a guarantee for Internet safety.
HTTP Secure, Wikipedia
What is HTTPS?, Instant SSL