Use “There” when you are referring to a location e.g. It’s over there. I remember it because if you remove the “t” you get “Here” which is also a location e.g. Here and There.
Use “Their” when you are referring to ownership. For example, It’s their home.
The word “They’re” is actually an abbreviation of the phrase “They are” e.g. They’re on holidays at the moment. To work out if you should write there or they’re, simply replace it in the sentence.
Right: They are on holidays at the moment.
Wrong: There are on holidays at the moment.
Have a grammar question? Ask Karen