Web Server is software that functions to receive requests from users via a web client or browser, then it will be responded by providing display/output according to the request sent to the server.
A web server is computer software and underlying hardware that accepts requests via HTTP or its secure variant HTTPS. - Wikipedia
For how it works like this, for example the client will access iqbal.id, then the web client sends a request to the web server and the web server receives the request.
Then the web server will read whether iqbal.id is in the configuration, if the iqbal.id configuration is found then the web server will look for the requested data.
If it is found, it will be given to the web server and the web server will send the requested data to the web client.
There are several software that can be used as a web server such as Apache, Nginx, then Lighttpd or lighty and many more.