Who is this? What is this?

Two questions, one answer shape

Russian splits what into two questions by whether the thing is alive. Кто это? asks about people and animals, Что это? about everything else. Both are answered the same way: Это plus the word.

There is no verb here, and no article either

Это книга has two words and means this is a book. Russian has no present-tense to be – the place where English puts is simply stays empty, and in careful writing a dash can stand there instead: Москва – город.

There is also no a and no the. Книга is a book, the book and book at once; which one is meant comes from the situation and from where the word stands in the sentence.

Это стол. Это книга.This is a table. This is a book.

Yes and no

To confirm or deny, the same sentence takes да or нет, and the negation particle не goes directly in front of the word it denies.

Нет, это не телефон.No, this is not a phone.