What does this mean by George B. Shaw?

Question

"The single biggest problem with communication is the illusion that it has taken place".

Answer 1

It means that many times even though we think that the other person understands us, they actually haven't got a clue.

Did you ever have a concersation with your boyfriend or parent where you thought that everything was settled only to find out that they didn't remember/weren't paying attention/ misunderstood?

Happens all the time.