A Gentle Reminder

It's = a contraction for it is or it has

It's not that difficult to learn the basics of your language.
It's not been that long since we've had this converstation.

Its = possessive pronoun

The bank is lowering its interest rate.
Education is its own reward.
Fox News is often up its own arse.
Some say Starbucks charges too much for its coffee.
This blog probably has run its course.

They're is the contraction for they are.

They're having knee-jerk reactions television pundits.
I don't agree with what they're saying.

There is a noun or adverb, usually indicating a place.

You can put it there.
Here is not always better than there, but there is not always better than here. Both places, in fact, have their own merits and weaknesses.
No matter where you go, there you are.

Their is a possessive pronoun.

All people are entitled to their own opinions, no matter how uniformed they may be.
My friends have graciously allowed me to sleep on their chesterfield.

Thier does not exist. Please do not use it.

One more example ...

Lucy and Ricky own a big mobile home. They are driving it across country.

They're going there in their giant camper van.

Thank you for your (not YOU'RE!) attention.

There will be a quiz next week.