HERE



it is the opposite of HERE: Where are the children? They are over THERE.
it shows that something exists: THERE is some sugar in my coffee.

THEIR
it refers to something someone has: They bought THEIR house in 2004.
it is always followed by a noun: THEIR car is in THEIR garage.


THEY'RE
= they are
it can be followed by:
an adjective: THEY'RE happy.


a verb+ing: THEY'RE working.

an adverbial phrase of place: THEY'RE in the garden.