Possessive nouns need an apostrophe to show ownership. Possessive pronouns do not.
Here are the possessive pronouns: my, your, our, their, his, her, mine, yours, ours, theirs, hers, its
The dog belongs to me, so the dog is mine. It is my dog.
The car belongs to Mary, so the car is hers. It is her car.
Mary drives her car. Bob rides his bike. The cat chases its tail.
Never use an apostrophe when writing a possessive pronoun.
▶It’s your turn. Choose a possessive pronoun for this blank. Do not use an apostrophe. John and Sue own a house. The house is ____. Wasn’t that easy?