“Calligraphy” means “beautiful writing” (or writing as a form of art). During the Middle Ages, the Muslims respected calligraphy as the highest art form because the Qur’an was written in Arabic and it represented the word of God. So calligraphy decorated the mosques and holy books of Islam. Writing was not only an artistic expression, it was a religious expression as well.
Over the centuries Arabic calligraphy expanded to include different styles of writing. Just like in English where there are many kinds of handwriting (printing, cursive, and even “graffiti style” writing), many respected writing styles in Arabic developed.