Complex sentence: It is what is learned in interaction with others and with the environment more generally, both about that environment (including society), but "also" about who s/he is: his or her'sense of self'.
Split into simpler sentences: It is what is learned in interaction with others and (more generally) with the environment. This includes both knowledge about that environment (including society), but "also" about who he or she is: his or her'sense of self'.