Different source of information are aimed at different audiences, that is indeed correct, because each particular audience has particular characteristics. The information needs to be adapted. What this actually means is that the language, style and structure of the information will vary and experience changes dependending on the audience that is aimed to, so that it will affect the audience in the intended way.
For example an encyclopedia of biology, if it's aimed at students from middle school, will have a very simple and clean structure, with friendly language and style, to make it easier for those students to understand. But if the encyclopedia of biology is aimed to college students, those element will vary to become more complex.
You mentioned that sometimes one source of information can be directed to more than one audience. This is also correct. The proper way to achieve this is by adapting the source a certain way so that it can impact both audiences in the intended way. To do this, each audience would have to share a certain characteristic or quality with the others. Have one or more elements in common so that the source can use those common elements and adapt in a way that its effect will work for both audiences at the same time.
For example, a TV commercial can show images of a new shopping mall in town. It the commercial includes images of nice lady stores but also a big colorful playground, both audiences (moms and children) can relate to that commercial, making them want to go together. That way, the same TV commercial (source of information) was aimed at two different audiences (moms and children).
The element that those audiences have in common is that both can understand images.
