Before we get into the nitty-gritty of how the pulse wave attack behaves, we must first define what a distributed-denial-of-service (DDoS) and denial-of-service (DoS) is, so we are all on the same page. Instead of regurgitating text from resources on the internet I have included a nice quote from Wired.
Simple DoS attacks, performed from a single machine, are uncommon these days. Instead, they’ve been supplanted by DDoS attacks, distributed denial-of-service attacks that come from many computers distributed across the internet, sometimes hundreds or thousands of systems at once. The attacking machines are generally not initiating the assault on their own but are compromised machines that are part of a botnet controlled by hackers who use the machines as an army to target a website or system.