I have heard people describe process communication as traffic on the data highway, but in this video it is well illustrated and the simple symbolism helps to explain it in a way that everyone can understand. In the video they are explaining the pros and cons of using PROFINET, showing the comm traffic as congested highways with many intersections and traffic light. Unlike PROFIBUS which uses a single lane means of communication, PROFINET works on a two lane highway for better communication that is faster and more efficient. But with the increase amount of communication traffic it does demand a higher network load.
Please take the time to watch this short animated video on PROFINET for a simple and informative look at the communication highway.