it plus 's means it is (the apostrophe takes the place of the letter i)
POSSESSIVE PRONOUNDS NEVER TAKE THE APOSTROPHE; ex.:
its is the possessive form of it: none of the possessive pronouns take apostrophes
ex. his, her & hers (not her's) as in the book is hers
thier & theirs (not their's), my, mine,
our & ours (the books are ours),
its = NEVER an apostr