What is the correct interpretation of the khuff, and is it permissible to wipe over it during ablution without removing it?

The Khuff: That which is worn on the foot, made of thin leather or similar material. Its plural is Akhfaf. It must cover the two ankle bones or more. Wiping over the Khuff is established from the Prophet, peace and blessings be upon him, both by his words and actions. This is the opinion of the generality of the people of knowledge, provided that it is worn after a complete purification.