Islam is the God's final message to humankind, a reconfirmation and perfection of the messages that God has revealed through earlier prophets.
A. Oneness of God: The central belief is that there is only one God to be worshipped, unique incomparable, eternal, absolute and without peer or associate. Allah is the name of the One and Only God in Arabic. The word Allah is used by Muslims, Christians and Jews alike who speak the Arabic language. Allah has ninety-nine beautiful names, such as: The Gracious, The Merciful, The Beneficent, The Creator, The All-Knowing, The All-Wise, The Lord of the Universe, and others. He is the Creator of all human beings. Muslims do not believe in the idea of a trinity or a unity with God which implies more than one God in one.
B. Oneness of mankind: God is the Creator of all that exists and that His will is supreme. People are created equal in front of the Law of God and there is no superiority for one race over another. God made humans of different colors, nationalities, languages and beliefs so that we get to know each other. The best of people are those who are pious and righteous.
C. Oneness of Messengers and the Message: God sent different messengers and prophets throughout the history of mankind in order to guide them.
Adam, Noah, Abraham, Isaac, Ishmael, Jacob, Moses, David, Jesus, and Muhammad, all came with the same message to worship the one true God. Some were sent books, such as the original Torah or the original Gospel.
However over time the true message was changed or misinterpreted or incompleted (eg. Jesus mission was incomplete).
By Muhammad(saw) (is the 'seal' of all the prophets -- that is, the last and final messenger from God) has completed the religion for the whole universe.
D. Angels and the Day of Judgment: Angels created by God in the universe for special tasks. Muslims believe that humans are responsible to God for their actions; and that, on the Day of Judgment, an all-knowing and merciful God will judge His creation according to their deeds in this life. On that 'day' all people of the world throughout the history of mankind till the last day of life on earth, are to be brought for accounting. The reward or punishment is to be Heaven or Hell.
E. Innocence of Man at Birth: Muslims believe that people are born free of sin. It is only after they reach the age of puberty and it is only after they commit sins that they are to be charged for their mistakes. No one is responsible for or can take the responsibility for the sins of others. However, the door of forgiveness through true repentance to God is always open.