How SSL certificates work

Without getting overly technical and in-depth, your browser goes through
four basic steps to ensure that the connection is secure:
1. It checks the address of the site and its IP address against the details on
the certificate.
2. The server and the browser interact to determine what encryption types
they can both support and agree on one to use.
3. The server and the browser supply each other with unique codes to use
when encrypting and decrypting data sent between them.
4. The browser displays a confirmation in the address bar that the connection is secure, and all data is then sent encrypted.
When a connection is secured, it uses a slightly different connection protocol known as HyperText Transfer Protocol Secure (https). This replaces the
standard http protocol and you will notice that the web address now starts

If the https://is colored red, it means the site is attempting to
use the secure protocol but the certificate is not valid or not recognized so the
connection may not be secure.