Imagine that you're at a conference, listening to various speakers about a wide range of interesting topics. Those you've listened to so far have been quite eloquent, and you have just arrived to yet another talk about - something. You're not quite sure, but if the other talks are anything to go by, this is sure to be well worth the listen.
But as the speaker gets going, it becomes clear that he really has no clue as to how this thing called public speaking works. He's obviously tying to sell something, but as the train wreck progresses, it becomes clearer that you are not going to find out what by listening to his utter lack of wordplay.
So you leave, and hit one of the nearby places with free conference food. It's not great, but it's free and it's food. That's good enough for the moment.
While there, you discover that you're not alone in this sudden relocation to greener buffet tables. Another listener from the talk you just left has found his way there, and you naturally fall into conversation about how awful the speaker was. In short order, you're talking and laughing like you've known each other for a lot longer than the mere moments you've actually spent in conversation.
Now ask yourself - which of these two have made the biggest impact on you? The overpaid speaker, or the chance encounter with the random stranger?
This is the difference between marketing and public relations. And you really don't need to go to a stuffy conference with terrible free food to spot the difference.