Not sure if this is responding to your question, but I hope it's helpful: In formal English, verb "to be" (am/is/are) uses "nominative (subject) case" (I/we/he/she/they) before & also after; in informal English, uses "accusative (object)" (me/us/him/them) after. Examples: It is I (formal) vs. It's me (informal). I am he (formal) vs. I'm him (informal). It is they (formal) vs. It's them (informal). [If you use the formal in speaking, it's technically correct but sounds a bit snobby or old fashioned.] For questions, using the accusative just sounds wrong: What/who/how am I; what/who/how is he; what/who/how are they--all sound fine. Using me/him/them in these sentences doesn't sound right.
@katerinasiap "Cosa sono?" is correct (what are they?, what am I?), "chi sono?" is correct (who are they?, who am I?), "chi cosa sono?" just like that, it's not possible to say, but "chi e cosa sono?" is correct (who and what are they?, who and what am I?). Obviously it depends on the context. Hope it's helpful.
I'm having an existential crisis right now due to this question. What am I? Are we here? Is life an illusion? Are we real? Is this a dream? How did we evolve from a one celled organism that used to photosynthesize, to being humans that use technology in everyday lives (for example to learn languages)? What is the meaning of life? Is there lore in mc?