Given the fact that some of these Islamic teachings and concepts have been forgotten by many Muslims, and given the fact that some of them have been given wrong definitions or interpretations by some non-Muslims, either deliberately or out of ignorance, an effort has been made here to present these teachings and concepts in their true light and clear picture.The definitions cover a wide range of concepts as well as some of the well-known Prophets and Messengers of Allah, may Allah's peace be upon them all, the significance of certain important Islamic occasions, the benefits of the observance of certain practices and a short biography of the four rightly-guided caliphs who helped shape the destiny of the new faith.Even though the present reference guide is designed specifically for Muslim children, readers and students of all ages and different faiths who wish to learn more about the world's fastest-growing religion will certainly find it enlightening and highly informative.