Distributed Denial of Service (DDoS) attack is a malicious attempt to affect the availability of a targeted system(s) or network. The offender initiates a lot of requests to overwhelming the target(s) and uses several compromised or controlled sources to launch the attack.
DDoS mitigation is the process of protecting a target from a DDoS attack successfully.
DoS attack uses a single system and one Internet connection to flood a targeted resource whereas a DDoS attack uses different systems and network connections to flood the target system..