While it's completely understandable if you never memorize the exact past participle or the present progressive form of "lie" or "lay," it's imperative to your happy life that you understand and internalize the meanings and uses of "there," "their," and "they're."
Their is a possessive pronoun that indicates ownership. Why did the Stellas bring their hippo to the picnic?
There is an adverb indicating location. What is B-Shaves doing over there?
They're is a contraction of they are. They're going to be surprised when they find out that Dr. Gonzo plans on removing their heads during today's surgeries in order to start a brain farm in the empty field. You know, the one over there.
*Please respond to me by using all 3 forms of the title words at least 3 times each in a lovely and exciting paragraph. I encourage exaggeration.
