fromEnglish Grammar Today
There,theirandthey’reare commonly confused in English, as they sound the same.
Thereis an adverb which refers to places:
The shop you need is overthere.
We also usethereto say that something exists:
Thereis a large oak tree outside the hotel.
Theiris a possessive determiner which means ‘belonging to them’:
Theirhouse is very small, isn’t it?
They’reis a shortened form of ‘they are’:
They’retoo young to have a holiday so far away from home.