Theology
Islamic theology (aqidah) is a branch of the Islamic sciences that has to do with what Muslims believe.
Correct belief is the foundation upon which Islam is built, and testifying that “nothing is worthy of worship except God”, and that “Muhammad is the messenger of God” is what makes someone a Muslim. There are core beliefs that every Muslim must know, and deeper nuances that require advanced study.
Importantly, in Islam, faith is consistent with the faculties of logic and reason.
For an introductory study of aqidah, see the following video playlist by Shaykh Muhammad al-Yaqoubi: