According to the text and notes, “the most basic belief of Islam”, or one of the two central tenants, concerns the identity of Allah.  In Islam, who is Allah?

In Islam, Allah is the Arabic word for God, and He is understood to be the singular, sovereign, and ultimate deity who is central to the Islamic faith. Allah is believed to be all-powerful, all-knowing, and merciful. One of the core tenets of Islam is the belief in the oneness of Allah, known as Tawhid, which emphasizes that there is no god but Allah and that He has no partners or equals.

Muslims regard Allah as the same God worshiped in Judaism and Christianity, though their understandings of His nature and attributes may differ. Allah is not depicted in human form in Islam, as the religion strictly forbids any representation of God to maintain His absolute uniqueness. Instead, Allah is known through His names and attributes, such as Ar-Rahman (The Most Merciful) and Al-Hakim (The All-Wise).

In summary, Allah is the sole and indivisible deity in Islam, characterized by His mercy and omnipotence, and is at the heart of Muslim faith and practice.