OK, by popular demand, here's the skinny on how to get this straight.
THERE is an indication of a place: Put the basket there. Go over there.
It can also be used with a "be" verb to indicate the existence of something: There is a house in the woods.
Rarer use might be in a greeting: Hey, there.
Rarer still it's used as a soother: There, there, nothing's broken.
THEIR is a plural, possessive pronoun used for ownership by more than one: Their team always wins. We like to get their ideas.
THEY'RE is a contraction of "they are." They are foolish. = They're foolish. Usually followed by a verb, noun, or adjective: They're running late. They're clowns. Their tall. Watch out for ends of sentences; won't work: I wonder where they are. You can't say, "I wonder where they're."