Port number 443
The HTTP protocol uses plain TCP as its transport mechanism, which is unencrypted and therefore can be intercepted by an attacker who is suitably positioned on the network.
HTTPS is essentially the same application-layer protocolas HTTP but is tunneled over the secure transport mechanism, Secure Sockets Layer (SSL). This protects the privacy and integrity of data passing over the network, reducing the possibilities for noninvasive interception attacks. HTTP requests and responses function in exactly the same way regardless of whether SSL is used for transport.
NOTE: SSL has strictly been superseded by transport layer security (TLS), but the latter usually still is referred to using the older name.