Liberalism and progressivism within Islam involve professed Muslims who have created a considerable body of progressive thought about Islamic understanding and practice. Their work is sometimes characterized as "progressive Islam". Some scholars, such as Omid Safi, differentiate between "Progressive Muslims" versus "Liberal advocates of Islam".

Islamic schools and branches have different understandings of Islam. There are many different sects or denominations, schools of Islamic jurisprudence, and schools of Islamic theology, or ʿaqīdah (creed). Within Islamic groups themselves there may be differences, such as different orders (tariqa) within Sufism, and within Sunnī Islam different schools of theology and jurisprudence. Groups in Islam may be numerous, or relatively small in size.