A kafir, (Arabic: كَافِرٌ) pronounced as, "kaafir", is someone who does not believe in God according to Islam. It is the most common description used in the Qur'an for non-believers or non-Muslims. A person who denies the existence of a creator might be called a dahri. Jews and Christians were required to pay the jizya and kharaj taxes, while others, depending on the different rulings of the schools of Islamic jurisprudence, might be required to convert to Islam, pay the jizya, be exiled, be enslaved or be subjected to the death penalty.
Kufr: Unbelief; non-Muslim belief (Kāfir = a non-Muslim, one who has received no Dispensation or Book; Kuffār plural of Kāfir).
To begin with, there was no forced conversion, no choice between "Islam and the Sword". Islamic law, following a clear Quranic principle (2:256), prohibited any such things [...] although there have been instances of forced conversion in Islamic history, these have been exceptional.