What is the name of the method/technology when a site is deployed on one domain and available on another?

Question

Network administration

I did not know how to clearly describe in one question.
Therefore an example.
There is an online learning platform ISpring (or Unicraft, that's not the point).
When a client buys access, he is given his URL, by which the client has access to his platform - someurl.ispring.ru
In the settings, you can specify that this platform is as if on the client's domain : virtual.skcu.kz

works, but I don't know what it's called to google it.
The closest I know is aliases, but is it something else? Like I can specify an alias for the account1.ispring.ru subdomain to redirect to virtual.skcu.kz . Are you wondering how it works in reverse?

Answer 1

reverse proxy or forward/reverse proxy
popular tool - nginx web server

Answer 2

This is the Domain Alias ​​in the HTTP server.
It's just that not only the main domain on ispring is registered in the settings, but also the client's domain. When an HTTP server receives an HTTP request, it looks for a domain name in the request. If the found domain name is in the configs, the server understands from which directory (assigned to the domain name) files should be taken. You can assign at least 100500 domains, they will all work with files in the same directory.
You can work under any domain name, or you can check that the request came to the correct, but unwanted domain name - and redirect the requester to the same URL, but with the desired domain name.