Что это? Кто это?
Ask кто это? when you talk about animate objects (that denotes persons or animals)
Ask что это? when you talk about inanimate objects (that denotes objects)
Notes:
1) Read more about the difference between animate and inanimate objects here - https://www.ruspeach.com/learning/2155/
2) мой, моя - are posessive pronouns, they change their endings because of the gender of the noun they go with. (read more about it here - https://www.ruspeach.com/learning/3371/)
Кто это?
[kto èhta]
Это моя мама.
[èhta maja màma]
Это мой папа.
[èhta moj pàpa]
Ask что это? when you talk about inanimate objects (that denotes objects)
Что это?
[shto èhta]
Это мой стул.
[èhta moj stùl]
Это моя книга.
[èhta mayà knìga]
Notes:
1) Read more about the difference between animate and inanimate objects here - https://www.ruspeach.com/learning/2155/
2) мой, моя - are posessive pronouns, they change their endings because of the gender of the noun they go with. (read more about it here - https://www.ruspeach.com/learning/3371/)