Classical Arabic is the language that is used in the Quran (Koran), and is considered holy by Muslims. Islamic people will not translate the Quran into other languages so that they can understand it better; instead, they will learn Arabic to fully understand a more genuine meaning of what is trying to be conveyed. If you wish to try to understand the holy religious text of the Quran, for whatever reason, then learning Arabic is your first step. Many religious schools, particularly in the Middle East are also almost entirely Arabic-speaking.