There, Their and They’re
You use “there” when you say where is the object or living thing. For example: Look! There is the Ice-cream truck.
Use “their” when you say something belongs to them. For example: That is not our Kitty, it is their Kitty.
“They’re” is short for “they are”. So when you are using it, if they are doesn’t make sense, “they’re” is not going to work either. For example: They’re going to the Movies.