The web application has two parts: front-end and backend, which can be located on different servers.
The backend server hosts PHP files, which deliver data for the web application.
One or more front-end servers can access a single backend server.
The front-end server hosts static HTML files and script
api.js. This allows
Default, front-end looks for backend on the same server, in the same directory, but you can specify a different location by using the element
<link id="server" href="http://vaskovsky.net/vtl/sample/en/" rel="preconnect"/>