HTTPS
Hypertext Transfer Protocol Secure (HTTPS) is an extension of the Hypertext Transfer Protocol (HTTP) for secure communication over a computer network, and is widely used on the Internet. In HTTPS, the communication protocol is encrypted using Transport Layer Security (TLS), or, formerly, its predecessor, Secure Sockets Layer (SSL). The protocol is therefore also often referred to as HTTP over TLS, or HTTP over SSL.
Virtual hosting
The default port number for HTTP is 80. However, most webservers can be configured to operate on almost any port number, provided the port number is not in use by any other program on the server. There is the HTTP Secure special port 443 that needs special configuration (see Server Name Indication). Port based web sites are explicitly bound to a unique port number and an IP address. In this case the IP address is used for hosting multiple web sites. The unique port number used for a common IP address distinguish an individual web site from other web sites bound to the same IP Address.