Is "il" a subject pronoun or " son"?? Or both?? Please explain?

Question

i was wondering can you use them both?

Answer 1

'son' means 'his' or 'her' or 'its' describing a masculine thing, as in 'son chocolat' - his/her/its chocolate.
'sa' means the same, but describes a feminine thing: 'sa fille' - his/her/its daughter
'ses' means the same, but describes a plural thing: 'ses yeux' - his/her/its eyes
These are all adjectives, because they are used to describe a noun (chocolat, fille, yeux). Specifically, they are called possessive adjectives because they indicate ownership.
In English as in French, the subject of a verb needs to be a noun or pronoun. So you can't use one of these demonstrative adjectives as a subject. 'Son aime nager' in French is as wrong as 'Its likes swimming' in English.
Example:
Grigri est le chat de Robyn. Grigri is Robyn's cat.
You can replace the subject noun, Grigri, with a subject pronoun (il/he), and you can replace the phrase showing ownership of the cat (de Robyn/Robyn's) with a possessive adjective (son/her)
Il est son chat. He is her cat.
But you can't say:
Son est il chat. Her is he cat.