At its best, advertising is story telling that sells a product or service. The story could be told through any number of channels, including online, tv, radio, outdoor, print, etc.
I use the term ‘story’ loosely. It doesn’t have to be a novel. The story could be told in one or two pictures. American Apparel is able to communicate quite a bit using only pictures.
The hero of the story should be the product or service that’s being sold. Notice how the polka dotted pants make the woman appear irresistibly sexy. Nice work, hero.
The story should elicit questions in the reader. The reader should be drawn in, curious about what is happening or what happens next. And most importantly, she should wonder what that product would do for her.
The less story-like an ad is, the worse it will perform. It should be noted here that an ad that only sticks to the boring facts is still an advertising. It’s just not advertising at its best.
I guess this article didn’t really define what advertising is, only what I think it should be. You may want to try Wikipedia for a more objective definition.