They’re always expand to they are
Only use they’re if you can substitute it with they are.
e.g. “They’re not leaving on Saturday now”
Their can often be substituted with our
Here is a little trick to test whether their is correct: Use the word our instead of their. If the sentence still makes sense, then their is almost certainly correct. This trick works because our and their are both possessive adjectives used for plurals.
e.g. “Can you show the guests to their cabins?”
There is similar to the word here in that it represents a place
It is used to denote a specific place.
- She is there.
(2) It is used to denote that something exists.
- There are two apples.