The difference between its and it's is like the difference between sweet and sour, summer and winter, Buffy the movie and Buffy the show.
Even so, EVERYONE STILL GETS IT WRONG. (And yes, we're yelling. This one makes us mad.) Here's how it goes:
The word it's is a contraction for it is or it has.
The word its is a possessive adjective that shows what it owns.
Need help remembering it?
That apostrophe in "it's" takes the place of something else—the second I in "it is" or the H and A in "it has." If you're not saying "it is" or it has," lose the apostrophe. Okay, okay—this isn't the case with other possessive adjectives, like Mary's hamster, the hamster's wheel, and the wheel's loose screw...so we understand why people mess it up. (Hey, we didn't invent English.)
Keep in mind that other possessive adjectives like her, our, and your don't end in S, though, so they never accidentally have apostrophes. If these ended in S, they'd be pronouns, like in the sentence: I didn't know what to do with yours. Confusing, we know.
"Perfect Pretzels, that gourmet pretzel store downtown, really lived up to its name."
"I really don't understand it's bad reviews on Yelp."
Which sentence is correct?
The first one. The possessive adjective its modifies the noun name to show ownership. The second sentence is incorrect because it uses the contraction it's when it should use the possessive adjective its to note that the bad review belongs to Perfect Pretzels.