"To have" is one of the most important English verbs. It has two conjugations in the present tense. The conjugation for the third person singular (he, she, or it) is "has." The conjugation for all other grammatical persons is "have."
I have
you have
he has
she has
it has
we have
they have
Usage
"To have" can be followed by a noun, past participle, or infinitive.
To have + noun
To have followed by a noun means to possess, own, hold:
I have two brothers
Do you have a pen?
I think he has a question
To have + past participle
This construction is called the present perfect:
We have already eaten
Have they tried to help you?
She has gone there three times
To have + infinitive
To have followed by the infinitive indicates something that is required, that must be done:
I have to study
We have to leave
He has to take a shower