‘Have’ and ‘has’ are both used to denote possession, form the perfect tense, and the past tense of both is ‘had’, but they are used differently.
‘Have’ is used with
- the following pronouns: I, you, we, they. Examples : 'I have a pencil.' 'We have a big house.'
- pluralised nouns: Example : 'Doctors have a rough time, dealing with illnesses all the time.'
‘Has’ is used with the third person singular (he, she, it). Examples : 'She has your money.' 'Amit has the book.'