A little something Yoshi-P said back on the 10th.

A DDoS (Distributed Denial of Service) attack overwhelms the target with an irregular amount of data, which causes servers and networks to become overloaded and cease to function properly. Because the irregular amounts of data are being sent from various sources all over the world, it is extremely difficult to trace or defend against an attacker.

For instance, imagine if an enormous number of people with fake tickets lined up for a concert. This would disrupt the workflow of the concert staff and prevent them from doing their actual tasks. Because a large number of people are coming from various locations at the same time, it would prove difficult to locate the person distributing the fake tickets or to prevent people with fake tickets from lining up beforehand.