Their, There, They're: The Difference, With Examples
Their is possessive, there is a place, and they're means 'they are.' Here is how to tell the three apart every time, with a trick for each.

These three sound exactly the same, which is why a spell-checker never catches them, they are all real words, just used wrongly. Once you know what each one actually does, they stop being a coin flip. Here is each, with a trick.
Their = it belongs to them
'Their' is possessive: it shows that something belongs to a group of people. Their house, their idea, their turn. Trick: 'their' contains 'heir', someone who inherits, owns, something.
There = a place, or 'there is/are'
'There' points to a place, or starts a statement about something existing. Put it over there. There are three options. Trick: 'there' has 'here' inside it, and both are about place.
They're = they are
'They're' is a contraction of 'they are', nothing else. They're late. They're my friends. Trick: if you cannot swap in 'they are' and keep the sentence sensible, it is not 'they're'.
They're going to leave their coats over there. → They are going to leave [the coats that belong to them] over [that place].
The Grammar Checker catches their/there/they're mix-ups a spell-checker sails past, and explains the fix so it sticks.
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