What is a DDoS attack and how does it typically affect an Azure Application Gateway?

A Distributed Denial of Service (DDoS) attack overwhelms a system with traffic, making it unavailable to legitimate users. For an Azure Application Gateway, this means a flood of requests can saturate its capacity, leading to slow response times, connection timeouts, and ultimately, service disruption. The attack targets the Application Gateway itself, its underlying load balancer, or the backend servers it routes traffic to.