_Its_ is a possessive pronoun.

_It's_ is an abbreviation for _it is_.

Do not use an apostrophe with the possessive adjectives _hers_, _ours_, _yours_, _theirs_, _its_.
2.

All nouns in the singular and all nouns in the plural except those ending in _s_ take an apostrophe and _s_ to form the possessive.
Nouns in the plural ending in _s_ take an apostrophe only to form the possessive.
There is much difference of opinion as to the invariability of the rule concerning singular nouns in _s_.

DeVinne advises following the pronunciation.