Its is a third person singular possessive determiner.
You use its to indicate that something belongs or relates to a thing, place, or animal that has just been mentioned or whose identity is known. You can use its to indicate that something belongs or relates to a child or baby.
The dog lifted its head, listening.
I met one woman whose tiny baby had just died and whose other child was fighting for its life.
1 It's is the usual spoken form of `it is'.
It's the best news I've heard in a long time.
2 It's is the usual spoken form of `it has', especially when `has' is an auxiliary verb.
It's been (has been) such a long time since I played.
He's got (has got) the guts to do it.
(c) HarperCollins Publishers.
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