"It's" and "its" are different from one another in the following literary ways.
"It's" is a contraction. Since "it's" has an apostrophe in place of the 'i' that would otherwise make the full two-word verb expression "it is", you can remember the mnemonic rule for contractions and apostrophe usages in that way with that literary example.
"Its" is singular-possessive. "Its" means "something that belongs to it". "Its" is unusual in the sense that it bends (if not breaks) the mnemonic rule of singular-possessive tense adjectives possessing apostrophes in their spelling to indicate that something belongs to the subject in question. ("His", "her", "hers", "our", "ours", "their", and "theirs" are also singular and plural-possessive adjectives that bend the given apostrophic rule of English.)
But if anybody writes "it's" when and where they should/intended to write "its" (and vice-versa), it will completely change the grammatical syntax of the written content at hand.