Wikipedia
The term hilya ( Arabic حلية (plural: ḥilan, ḥulan), (plural: hilyeler) denotes a religious genre of Ottoman Turkish literature, dealing with the physical description of Muhammad. Hilya literally means "ornament".
They originate with the discipline of shama'il, the study of Muhammad's appearance and character, based on hadith accounts, most notably Tirmidhi's al-Shama'il al-Muhamadiyyah wa al-Khasa'il al-Mustafawiyyah ("The Sublime Characteristics of Muhammad").
In Ottoman-era folk Islam, there was a belief that reading and possessing Muhammad's description protects the person from trouble in this world and the next, it became customary to carry such descriptions, rendered in fine calligraphy and illuminated, as amulets. In 17th-century Ottoman Turkey, hilyes developed into an art form with a standard layout, often framed and used as a wall decoration.
Later hilyes were also written for the first four Caliphs, the companions of Muhammad, Muhammad's grandchildren ( Hasan and Hussein) and Islamic saints ( walis).