Port 443 also known as HTTPS. The port that our web browser use for a secure connection. You might already know this but when open your web browser and type it a domain name your browser opens the requested site. If you look at the beginning of the URL you will notice the protocol that currently uses.
HTTP vs HTTPS:
In general, if you see the HTTP at the beginning of the URL, it means that the site is on a NON-secure connection. While a URL that begins with HTTPS is using a secure connection, you can search for the lock near the URL.
Although you do not see it, When your browser opens a URL it adds a port number to the end of the URL. An example of this in an HTTP connection will be http://sitename.com:80 or for HTTPS it will be https://sitename.com:443.
HTTP means HyperText Transfer Protocol.
HTTPS means HyperText Transfer Protocol Secure.
The HyperText Transfer Protocol is the underlying protocol used by the World Wide Web. It contains the definition of how messages are formatted and transmitted between client to the server and vice versa. The protocol also defines what actions Web servers and clients (browsers) should take in response to various commands. You can read more about the HTTP protocol on RFC 2616.
Server-side port 443:
If we are looking from the server-side, after all when you open your browser and surf toa website, There is on the other side a web server that handles the connection and a lot of other stuff. There is a listener on the webserver that waits for an incoming connection. HTTP is listening on port 80 and for HTTPS it listening on port 443. Once the connection is established the rest of the communication can be continued. Encrypted – on Port 443 or not encrypted on port 80.
Please note, port 80 and port 443 are the default port that had been assigned for the HTTP and HTTPS communication by the Internet Assigned Numbers Authority (IANA).