It's kind of like a membership to a club. You can see some of the symbols on various websites. People and companies pay to be a member of these clubs. Basicall

It's kind of like a membership to a club. You can see some of the symbols on various websites. People and companies pay to be a member of these clubs. Basically, it's saying that no one is going to step on each other's toes. Not being a member would make things hard for you to do business. This obviously isn't universal to all industries. As far as I know there are no written legal codes, so it's basically an example of self-policing a la libertarianism, where you pay to play and follow the rules.