If you look at a map of the middle east you see that it is mostly desert. In modern times it doesn't really effect us, but around 1500 years ago this effected the people who lived their greatly. Because of the harsh climate and terrain, it made it hard to grow crops and raising domesticated animals. Because of these factors it made it almost impossible to stay in one place, so their solution to this was becoming nomadic. Nomadic means never staying one place for a long period of time, always traveling from destination to destination, "Living of the land."
Later on these nomadic people would be called the Bedouins. They lived by traveling from oases to oases, since they provided water and shelter from the desert. After some time these oases became villages and trading points for nomadic people. Later on the middle east became completely dependent on trade since they where in the perfect place to trade from the byzantine empire to the Indian empire making them rich and prosperous. When Muhammad started speaking of the Muslim faith it spread around rapidly because of how it appealed to the poor and excluded and how since trade spread knowledge and ideas around.
The spread of Islam was slow at first because some people didn't like the idea of one true god, so the Muhammad and his followers where ostracized from trading points and settlements, except for one town were he was invited by the leader. There the Muhammad and his followers took refuge. A pagan tribe of 1000 fought the Muslims with only 300. Surprisingly the Muslims won and continued to conquer towns and cities soon they became 10,000 strong and took mecca. This was the beginning of the Muslim empire.
