Do you know the difference? These three words are homophones and they confuse many people.
their (possessive adjective), e.g. The boys lost their game against the girls.
there (adverb) = in/to/at that place, e.g. They played the game over there.
here (adverb) = in/to/at this place, e.g. Please come here.
They’re = they are, e.g. They’re due to arrive at 8:00 pm.