Empty vessels make the most sound
You will always find that a person with very little learning loves to jabber all the while and laugh and joke and make a lot of unnecessary noise. This is because the person doesn't really have any substantial matter in their head and so hides this fact with a lot of meaningless chatter. But the person of real substance looks around, observes and when he or she speaks, it is to say something really meaningful. That is what is meant by this proverb.
Hence when we are in a conversation we should only take a fair share of the conversation and not keep prattling on as if no one else is there. This will show that we respect other people's opinions and wish to hear them out too. It would also send out the message that we are not superficial people who only bore others with our pompous talk.
Difficult Words
Jabber: To talk rapidly and excitedly but with little sense; to chatter.
Substantial: Of considerable importance, size, or worth; having substance or reality.
Chatter: Incessant, trivial, or meaningless talk.
Meaningful: Having a serious, important, or useful quality or purpose.
Proverb: A short, well-known pithy saying, stating a general truth or piece of advice.
Prattling: Talking at length in a foolish or inconsequential way.
Superficial: Appearing to be true or real only until examined more closely; lacking depth of character or understanding.
Pompous: Affectedly and irritatingly grand, solemn, or self-important.