"There", "their", and "they're" - what's the difference?

• "Put it over there." (location)
• "There is a problem." (introducing)

• "It's their car."
• "Their opinion matters."

• "They're coming tonight." = They are coming.
• "They're not sure yet."

• Can you say "they are"? → they're
• Does it show ownership? → their
• Is it a place or introducing? → there

• "There" contains "here" - both are places
• "Their" contains "heir" - an heir inherits (possesses) things
• "They're" has an apostrophe showing letters are missing

This is one of the most common written errors in English, including among native speakers. Spell-checkers often miss it because all three are real words.