The Nicene Creed is the symbol and statement of our Faith. The Creed is a comprehensive summary of all the beliefs of the Orthodox Church. These truths were written and affirmed by First and Second Ecumenical Councils.
For a wonderful explanation of all the statements of the Nicene Creed, see The Law of God written by Father Seraphim Slobotskoy with excerpts available online here (scroll down to #4).
An excellent resource for both young people and adults is The Nicene Creed for Young People by Father Anthony Coniaris available here.