"Its" is a possessive pronoun like his/her/their/our/whose. "It's" is a contraction of "it is", hence the apostrophe. Any time you could grammatically say his/h

"Its" is a possessive pronoun like his/her/their/our/whose. "It's" is a contraction of "it is", hence the apostrophe. Any time you could grammatically say his/her/their, you should use the version without the apostrophe. Any time you could say "it is", you should use the version with.