The two main ideas that Mohammad received were Tawhid and the Quran. Tawhid refers to "the oneness of God." and designed to address the idolaters through Arab society at this time. This was chiefly accomplished through the entrance of the new Muslims (those who submit to God) into Mecca where Mohammad destroyed pagan statues in many shrines throughout the city. There was one black stone that was spared, later finding a place at the center of the Kaaba, the mosque in Mecca that was said to be originally built by Abraham.
Second was the Quran, which was the totality of the passages revealed to Mohammad by the Archangel Jibril (Gabriel) over a 23 year period that form the basis of the Islamic religion. The book itself is made up of chapters called suras and contains no actual laws (such as the Ten Commandments) but merely suggestions. It was the later Hadith (teachings based on interpretations of the words of the Prophet) that should be addressed when dealing with any inconsistencies (perceived or otherwise) in Islamic law or similar. The Quran is also considered to be the finest piece of Arabian literature in history.