Original: It comprises the Zanzibar Archipelago in the Indian Ocean,  off the coast of the mainland, and consists of numerous small islands and two large ones: Unguja (the main island, informally referred to as "Zanzibar"), and Pemba.
Simplified: Zanzibar  is the name for an archipelago in the Indian Ocean 25–50 km off the coast of East Africa, of numerous small islands and two large ones: Unguja (the main island, sometimes informally referred to as 'Zanzibar'), and Pemba Island.