its its, stupid.
means "it is" (or "it has")
It's embarrassing how you acted in that meeting today.
pretty much every other application of the word
Be easy on the Xerox machine; its exterior is durable, but can only take so much.
now that we've cleared that up, make sure you know:
you're: means "you are"
You're terrible at cold calls, Mr. Bigby.
your: belonging to a person
Please remove your compact disc from the optical drive prior to shutting down for the evening.
they're: means "they are"
They're going to come over for olives and chips in the board room to discuss fonts for our newsletter.
there: a place or position
I need you over there in the lunch room, we're about to sing happy birthday to Doris.
a reference to something that exists
I encourage you to participate in the team building exercise after work; there will be snacks.
their: belonging to people or things
Can you page the marketing team? We need their opinion on these spreads.