The spread of Islam and the conquests made by the Arabs brought major changes to the lands that the controlled. In this answer, I will look at two kinds of change that occurred. One was change that was brought about by the spread of the Arabs while the other has specifically to do with changes brought about by the spread of Islam.
Bentley and Ziegler say that the Arabs brought about the spread of various new crops and agricultural methods throughout their empire. They took crops that had been present in one area and introduced them in other areas. They spread ideas about how to farm more effectively. By doing so, they increased agricultural production. This led to a situation in which urban growth was possible because more food was available to feed city dwellers.
Bentley and Ziegler also say that the Arabs spread specifically Islamic values around their empire. Muslim missionaries, judges, and teachers spread out across the empire. They started to impose Muslim law and Muslim values on other people by, for example, resolving disputes according to the Quran and to sharia law. They also helped to spread their values through educational institutions that they set up. They set up schools at many mosques, thus spreading education that was given from a specifically Muslim point of view.
Thus, the spread of Islam changed the areas that came under Muslim control both in economic ways and in cultural ways.