this is used about "someone who is really young and inexperienced; kind of naive." ;) look at the sentence below: he is taking his first steps in this business, he is still wet behind the ears. or he is so inexperienced to be wet behind the ears.

When a person is born they are cleaned and dried. If the person is not dried well, they are still wet behind the ears. Say their when someone is acting inexperienced: Do not blame her for burning the cake. When it comes to baking, she is wet behind the ears.

Thank you! :)

naive. If someone has no experience in something, or if they assume something about the subject that is way off, then they're " wet behind the ears" but nobody uses this anymore. just say " you are so naive".