In “The medium is the message”, McLuhan was saying that the medium is the tool that we deliver information, and it is not the content but the media was the message that we were delivering. Also, it is the medium where rapid change is occurring. When people invent something new, they do it with the intention of simplifying our tasks or just with a good intention. However, throughout its process some face with negative consequences and some intentions are forgotten. The author is saying that the content of the medium, the new inventions, is itself an another medium.
before we use to distribute information by mouth, and then by newspaper, and now we do it by the use of the internet. So, our perception of the information is changing while this constant change is happening, and he suggests that if we pay attention to this changes and how it is affecting our society, we might be able to predict future effects before they happen.