explicitly taught (what's the meaning?)
Linguistic input available for a first language learner is utterly insufficient to build linguistic structures of the language he or she is going to speak. Not only are these structures extremely complex, but the set of possible utterances is unlimited, so that one may wonder how a child’s poor linguistic experience may prepare him or her for such a complex and infinite diversity. It is equally stunning how a child learns not to produce ungrammatical utterances, although he is extremely rarely, if ever, EXPLICITLY TAUGHT what is wrong.
Can anybody explain what EXPLICITLY TAUGHT means? I can't figure out the meaning of this part of the sentence "...although he is extremely rarely, if ever, EXPLICITLY TAUGHT what is wrong."