What does "under the application" mean?
Where PaaS differs is that it places the responsibility of managing and scaling the infrastructure beneath your application. This removes most of the day-to-day responsibility of managing the platform that delivers your application and changes many of the costs to ‘as consumed’ rather than for the compute you use (which may be under-utilised or over provisioned). On-top of this, if you choose to use Azure’s AppServices you are then able to use tools like Application Insights to start getting granular insight through deep application performance monitoring.