His post was a lot less "flooding" than most of the posts I've seen here. As a matter of fact, you just telling him to go to Google is a lot more flood-like than his original post.
Anyway.. To answer his question.. A DDOS (distributed denial of service) is when a massive number of people or IP requests go to a website in an attempt to bring it down. Usually these "hits" (which are more often than not fake) request a packet from the server over and over and over again in order to flood it's internet connection, which in method, cuts the website off from actual requests from actual people.
There's a term out there called "slashdotted" which is actually kind of funny.. Since /. is such a popular news website, usually when they link to an article on another website, the sheer amount of hits the website receives causes it to go down, which in theory is just like a DDOS attack. So many people trying to access the website that it gets overloaded and can't handle all of the requests. This is pretty much like a DDOS attack. When a program/script overloads a website's internet tubs and causes it to go down and not be able to send legitimate requests to legitimate visitors.