Islam religion is spread all over the world. However, Islam religion is major religion in the Middle East, North Africa, and Asia.
All over the world
Islam is spread all over the areas of the world although with different percentages.
christians
The Ghana Empire (which is in the modern countries of Mali and Mauritania) learned of Islam due to their trade relationships with Berbers and Arabs along the northern coast of Africa. The merchants from these areas were Muslims and brought their religion with them. As Islam was a stronger and more codified religion than those practiced by the Ghanians, Islam spread quite quickly from those interactions, dominating the territory by the mid-900s C.E.
Persia, India, Europe
nearly all regions of earth have Muslim people and Islam is spreading all over the world.
In most instances they did not and do not seek to proselytize. The spread of their religion occurred as Jews settled in those areas.
Islam was affected by trade routes when they traded too. For example, when Islam traded in westAfrica, they told the people there about the religion of Islam and they converted to it. It was affected by growing bigger on trade routes.
If you mean areas of land that are influenced by spread of Islam, then the answer is: Middle East, North Africa, Indian subcontinent, and South East of Asia.If you mean areas of human life and relationships, then the answer is: polytheism, woman human rights, racism and discrimination, tolerance and forgiveness, and science research and development.
Islam as a religion was not actually spread by Arab armies at all; it was spread by (1) using discriminatory legislation within territories controlled by the Arab Islamic Caliphates to promote conversion to Islam and (2) sending missionaries and business people to areas outside of the Caliphates to convert foreign dignitaries and subjects.As for "Islam" as a euphemism for the countries where Islam was an official religion, these empires ONLY expanded through conquest. Unlike European dynasties where territories would be added or subtracted based on strategic marriages, the leaders of Islamic Empires intentionally married women who had no nobility or claims to territory to prevent the rise of a potent aristocracy with familial connections to the throne.
That would be Christianity.