They’re is the contracted form of They are.
- They’re playing. (= They are playing.)
- They’re running. (= They are running.)
There is a kind of preparatory subject. It is used in sentences which say that something exists somewhere.
- There is a bridge over the river.
- There is no way out.
- There are two people in the room.
Their is a possessive word like my or your.
- I have been to their home.
- I would like to buy their car.