WebURK without any kind of subdirectories

It is my first time seeing something like this.

Does anyone know, what the name/kind/type of the website is that does not have any kind of subdirectories on the web-URL page, and it always just stays as a plain domain name, and how it was made, and how it can be avoided since I need to send an API call to one of those subdirectories?

Example: I have a website let's call it:

hello-world.net

it has UI page and it has a home page, which should look like this in a browser:

hello-world.net/home

or it has a /shipment option inside of the UI page.

so URL should look like this:

hello-world.net/shipment

and it has one more subdirectory inside for example /report, and if I select it, it should look like this: hello-world.net/shipment/report (something like this).

And open up that subdirectory, but again web-URL link on a website continues to stay just as a

hello-world.net

all the time.

And for some reason whatever subdirectory I would go on a website, Web-browser URL will remain as a hello-world.net all the time without any kind of changes subdirectories on a web-browser URL.

It is an internal website, so I can not post examples of it from work here.

Does anyone knows, what the name of that kind of set? How it can be avoided? Since I need to send an API request to one of the subdirectories?

I am not a developer, and I am new to IT, so I am not really sure, what the name of this, and how does it works.