The request starts when a user makes a request, this can be anything from clicking a link somewhere, entering a URL manually or some background AJAX request. This fires off an HTTP request that can have many "verbs", which tell the server what kind of action the client wants. The most common ones are get, post, put delete. There are other important ones such as patch and head. Once the request reaches the server, it is handled by the HTTP server, which is usually an apache or nginx server, these then redirect the trafic to the correct IP and port. At this point, it purely depends on the backend language and the archietecture that is being used, whether that be classic MVC or microservice but also say if PHP, or a templating engine is being used which requires the page to be interpreted after the .php or similar was fetched.