Based on this, and with the believe that knowing what we do not know can lead to better students (and better teachers) by improving cognition and metacognition, we will try to succinctly show a small part of what we know, but especially what we do not know about how to define the chemical bond and understand its existence. We cannot and will not be extensive, since the chemical bond field deserves an encyclopaedia. As such, we might leave more questions than answers, which is not necessarily a bad thing. As this article discusses a highly controversial topic, numerous researchers do not agree with many concepts postulated here. Again, this is not necessarily bad, as it shows the living disputes in this field which advanced chemistry students should also be aware of.