‘Be’ is an irregular verb. It is used as a main verb and an auxiliary verb. It is used as a main verb when it is the only verb in the sentence. Like every other verb it has its three forms :
Present : is, am, are
Past : was, were
Past Participle : been
It is used as a main verb :-
1.To indicate the role or position that one holds at work, other organizations or in a family.
Example 01 : Jennifer is my sister.
Example 02 : Mr. Baker was the chief guest at the award function last year.
2.Together with adjectives to express qualities about someone or describe someone.
Example 01 : She is an intelligent girl.
Example 02 : Marc is a handsome man.
3.To indicate a location.
Example 01 : They are at lunch.
Example 02 : She is in the laundry.
4.With the comparative or superlative form to make comparisons between people, places, objects and ideas.
Example 01 : Peter is shorter than Ben.
Example 02 : I am more intelligent than my brother.