We use an apostrophe (‘) to show that a noun owns something. We call it “having possession.”
Bob owns a car. The car is Bob’s car. We attach an apostrophe to the noun Bob to show his ownership of the car. The noun that comes right after the apostrophe noun is the thing that is owned. Since it is Bob’s car, we say that Bob‘s is a possessive noun – it shows Bob’s ownership. He owns the car.
Here are more examples of possessive nouns:
Mary had a little lamb. The lamb is Mary’s lamb.
Dad has a new office. The new office is Dad’s new office.
Sam has bike. The bike is Sam’s bike.
If a noun has an apostrophe in it, that noun is a possessive noun. That possessive noun has ownership of whatever word comes after the possessive noun.
▶It’s your turn. Find the possessive noun in this sentence. I took a ride in John’s new car. Do you see the noun with the apostrophe in it? That noun is showing possession. John owns the car.