When we join together the words they are, we get the contraction they’re.
Every time we use the contraction they’re, we really mean they are.
They are going to be late.
They’re going to be late.
The word their is a pronoun showing possession.
The cat is their cat.
I am going over to their house.
Use the contraction they’re when you are trying to say they are. Use the possessive pronoun their when you want to show ownership.
▶It’s your turn. Decide if you should use they’re or their in this sentence. My neighbors showed me ___ pretty garden. Did you figure out that the word for the blank should show ownership? Good for you!