Why are there so many sites in the IIS server that can share a 80 port?

Not to say on a machine, can only make a website with 80 port, but I found on this server, a lot of sites share a 80 port, I understand wrong

Reply to discussion (solution)

name-based Virtual Host
Https://httpd.apache.org/docs/2.2/vhosts/name-based.html

A service process uses port 80
Rather than a Web site
There can be n virtual sites in a service process

Set different "host Headers" for different websites

IIS is much simpler to set up a virtual host than Apache

Access to a port 80 is only external to the IIS service through this port
The IIS service has a virtual host: Access the host again through this

