'To be' expresses existence, identity, and states. It links a subject to information about that subject. It functions as the main verb in sentences like 'I am here.' It also acts as an auxiliary verb to build continuous and passive forms.

In the present simple, 'to be' has three main forms: 'am,' 'is,' and 'are.' The choice depends on the subject of the sentence. These forms state facts, descriptions, and general truths in the present.

Subject	Form
I	am
You	are
We	are
They	are
He	is
She	is
It	is

In the past simple, 'to be' has two main forms: 'was' and 'were.' Use 'was' with singular subjects and 'were' with plural subjects and 'you.' These forms describe past states, situations, and identities.

Subject	Form
I	was
You	were
We	were
They	were
He	was
She	was
It	was

The future simple uses 'will be' for all subjects. 'Will be' expresses future states, plans, and predictions. The structure remains the same regardless of the subject.

Subject	Form
I	will be
You	will be
We	will be
They	will be
He	will be
She	will be
It	will be

In spoken and informal written English, 'to be' often appears in contracted forms. Contractions make sentences shorter and more natural in conversation. The meaning does not change when using contractions.

Word/Phrase	Definition
I'm	'I'm' means 'I am' in a contracted form.
You're	'You're' means 'You are' in a contracted form.
We're	'We're' means 'We are' in a contracted form.
They're	'They're' means 'They are' in a contracted form.
He's	'He's' means 'He is' in a contracted form.
She's	'She's' means 'She is' in a contracted form.
It's	'It's' means 'It is' in a contracted form.

'To be' changes form for tense and subject. Present uses 'am,' 'is,' and 'are.' Past uses 'was' and 'were.' Future uses 'will be' for all subjects. Contractions are common in everyday English.