What is meant by Khulʿ and Faskh?

Khul' is the removal of the husband's ownership of his wife's marital bond and the dissolution of the marriage between them in exchange for compensation paid by the wife, if the wife is harmed by remaining with him and fears that she will not be able to observe the limits of Allah. The proof of its permissibility is His Almighty قول: "And if you fear that they will not be able to observe the limits of Allah, then there is no blame upon them for what she gives up to be freed thereby."

As for annulment (faskh), it is the dissolution and abrogation of the contract, either because the contract was originally invalid, or for another reason deemed appropriate by the judge.