These cute babies are playing and one of them appears to have milk teeth developing. Another is attempting to evaluate whether Charlie can really bite.
Charlie tries everything which enters his mouth. Probably, he thinks whatever enters his mouth needs to be bitten and eaten.
He doesn't know whether he is being tested. But, the noise which his friend makes implies to Charlie that something is wrong. This leads Charlie to letting the finger loose.
It is a video which is how children start learning concerning how to bite.
They test whatever is defined in their mouths. The elder child seems to report whatever Charlie is doing to a person nearby. Probably there is a parent nearby and that he is reporting Charlie. This is a fun video which shows how children can be aggressive and try to learn from the other when left to try out.