Their, there, and they're are all pronounced the same way. Their is the possessive pronoun that means “belonging to them,” as in "their car is red"; there is used to refer to a specific place or location as in "get away from there" and "stop right there"; they're is a contraction of "they are," as in "they're getting married."

“ There ” has a lot of different jobs that express slightly different meanings. As an adverb: She stood there waiting for cake even after we told her the dog ate it. As a pronoun: Hi there! As a noun: Once you finish the report, she’ll take it from there. As an adjective: I’ll be there for you, no matter what.

There can be used as an adverb, pronoun, adjective, and sometimes as an interjection. But in grammatical constructions like there is or there are, there is considered an expletive.