Their shows possession.
That is their house.
There shows position.
You live over there.
They're is a contraction of they and are and shows action.
They're playing the game.
A long way to write 'their' is by saying 'it belongs to them.' That house belongs to them. That is their house.
A long way to write 'there' is by saying 'in/at that place.' You live over at that place. You live over there.
A long was to write 'they're' is by saying they are. If the sentence makes sense when you use the word non-contracted, then you use they're. They are playing the game. They're playing the game.
YOU ARE READING
Grammatically Correct
RandomRules of writing so you are grammatically correct because it's one if my pet peeves. This is to educate and assist people in perfecting their writing and because school doesn't always teach us what we want to know.