В Present Simple глагол to be принимает 3 формы: am (для I), is (для he и she) и are (для you, we, they, etc.)
В Past Simple глагол to be принимает 2 формы: was (для единственного числа) и were (для множественного).
I am a Russian student. You are an English student.
Yesterday they were at home.
We shall be good students in some years.
