What does the term Taharri mean in Hanafi Fiqh?

Taharri: Choosing among Mixed Pure and Impure Vessels or Clothes

• Wiping over leather socks during Wudu.
• Putting deliberate mental effort to investigate and determine the pure option among mixed, indistinguishable items.
• Washing the limbs exactly three times.
• Draining all the water from a well.