"qui" means who. Here are examples that will help you understand how to use "qui". It is the same as in English:

• Qui est le propriétaire de la voiture ?
  Who is the owner of the car?
• Qui est-ce ?
  Who is it?
• Qui est cette femme ?
  Who is that woman?
• Qui peut dire une chose pareille ?
  Who can say such a thing?