Speaker and Listener

I tried to explain to my son what I was doing when I faxed a sheet of paper. He asked me what was happening. I said I sent the same sheet of paper to another office far from our house. I tried to explain that the fax was like a telephone, but instead of talking and sending our voices over the lines, we were sending sheets of paper. I am not sure he fully understood.

If not, it would be easy to say the reason was because he is just a young kid who lacks the maturity to understand. But is the listener at fault? Could the speaker instead be at fault? I, as the speaker, perhaps might need to be more clear in my explanation. Perhaps the problem is with the speaker rather than the listener. As speakers (and writers), we should always keep this in mind.