xD But if you really don't know, it's basically abusing something that works over the internet, to either get a message across or to create general annoyance. Y'know that Monty Python 'Spam' sketch? How the vikings constantly chant 'Spam' to drown out everything around them and get themselves noticed? That's what a spammer basically does, flooding in their normally-useless messages to an un-wanting crowd. Oh, and it's also 'Specially Produced American Meat'.
bottom line useless posts that really dont benefit anyone. theyre fun, and thats the only reason for it, fun.
If you have a debate on whether gay people should be allowed to marry or not. (Just an example, I do not have anything against gay people.) And if someone replies with f.ex "lol" it is spam. or just non-sense posts, and posts that clearly shows a desperate need to bring up post-count.