Homophones are words that sound the same but have different meanings. The different meanings often have different spellings.
The words there, their and they're are homophones.
Their means 'belonging to them'.
Susie and Sam have lost their puppy.
They're is short for 'they are'.
They're searching for him now.
There is used when we are talking about a place.
'He's over there!' shouted Susie.
We also use there when we say 'there is' or 'there are'.
'There is another puppy with him,' said Sam.