What are exactly Autoscale Incoming Requests?

In my account information there are quite obvious KPIs like data transfer or data storage.
But about Autoscale, i can’t explain one specific KPI : Incoming Requests

When a user comes on one of my deployed repl, what should count as a request ?

The request of the web page + css + favicon + each image on the web page ?
Is there an easy way to trace those requests ?

And of course it would be nice if all deployed repls could show the current amount of incoming requests