The meaning is: build something good, and people will naturally come to it. As opposed to: build a monster no one needs then spend millions on marketing.
As far as I know, Facebook and Google are both examples of following this advice. They both didn't reply on marketing to grow. They grew organically; people started to use them because they were actually good products.
I always thought this mantra originally came from Google.
There was a serious, real need for Google. All other search engines before Google were pretty much porn/spam laden. It was too difficult to find anything.
I'm glad not everyone listen to this advice, otherwise we wouldn't have Twitter, Facebook, or even Google.