how does replacing http:// with https:// in the URL manage to jump the firewall?

Answer 1

HTTP and HTTPS are different protocols, using different ports for the traffic. HTTP uses port 80, while HTTPS uses (by default) port 443. A firewall can be configured to block traffic through particular port(s) and to allow it through other(s). If it is configured to block port 80 but allow port 443, an HTTPS communication request (used by your Web browser when you enter an "https://" URL) will pass through it, while an HTTP communication request will not. Of course, the server you're communicating with must have valid content at that URL.

Answer 2

the extra added S means security.