DDoS
In plain terms
An attack that floods a service with traffic to knock it offline.
Going deeper
A Distributed Denial of Service uses many compromised machines to overwhelm a target's bandwidth or resources, making it unavailable to real users. Defenses include filtering, rate limiting, and scrubbing services.
Under the hood
Volumetric, protocol, and application-layer attacks differ; mitigation combines upstream scrubbing, rate limiting, anycast, and CDN absorption.
Examples
Botnet floods, SYN floods, the Mirai botnet, Cloudflare/AWS Shield protection.
Think of it like...
Like thousands of fake callers jamming a hotline so genuine customers can never get through.