From the beginning, the Islamic Empire was a monarchy like the Roman Empire or the Sassanian Empire before it. One man ruled the Islamic Empire. In the beginning, people called this man a caliph (KAY-liff), and his assistant was a vizier (vizz-EER). Those were Arabic words for leaders and their assistants. Under them were governors for each province of the Islamic Empire. But each town continued to have its own city council, too. All of these rulers were men, because the Islamic government didn’t allow women to get political power.
Later on, as the Islamic Empire broke up into smaller kingdoms, these less-powerful rulers kept the title of caliph. The Umayyads in Spain had a caliph, and the Fatimids in Egypt did too (though the real power in later Fatimid Egypt was in the hands of the army generals). But by around 1000 AD, new rulers tended to be called “sultan” instead, which was a Turkish word for a ruler. The Ayyubid and Seljuk rulers, the Hafsids and the Marinids called themselves Sultans. The Mongols called their leader a Khan (KANN). After the collapse of the Mongols, the Ottomans called their leader a Sultan again. But the assistants were still viziers. These viziers were very powerful men (they were nearly all men), and they often were really more powerful than the caliphs or sultans.
At first the Islamic Empire paid for roads and soldiers with the plunder that its soldiers took when they captured more land. When they stopped conquering new places, about 750 AD, they had to find a new way to raise money, and like other empires they began to collect taxes. At first, the Islamic caliphs only collected taxes from men and women who weren’t Muslims – from Buddhists, Zoroastrians, Manichaeans, Christians, and Jews. Even once these people did convert, the Islamic government kept on trying to tax just them, calling them mawali – Muslims who weren’t Arabs. But once most people had converted to Islam – partly to get out of paying taxes – the government had to start taxing Arabs too.