This is the 12265th most frequent Russian word.
исламского
"Islamic."
In this sentence, "исламского" is used as an adjective describing "мира" (world), conveying the meaning 'pertaining to Islam'.
Исламского мира насчитывает множество стран с богатой традицией.
The Islamic world comprises numerous countries with rich traditions.
Here, "исламского" is used to define the attribute of "периода" (period), denoting a historical timeframe associated with Islam.
Он изучает письменные памятники исламского периода.
He studies the manuscripts from the Islamic period.
In this context, "исламского" qualifies the term "искусства" (art), highlighting the art style that originates from Islamic traditions.