Positive
| I | have | a dog. |
| He/ She/ It | has | |
|
We/ You/ They |
have |
Negative
| I | don't have (do not have) | a car. |
| He/ She/ It | doesn't have (does not have) | |
|
We/ You/ They |
don't have (do not have) |
Question
| Do | I have | the keys? |
| Does | He/ She/ It have | |
| Do | We/ You/ They have |
Negative and question forms need the auxiliary verb 'do'.
In this case the auxiliary verb 'do/does' doesn't have any meaning.