Yap is an island in the Caroline Islands of the western Pacific Ocean, the westernmost state of the Federated States of Micronesia. The "island" of Yap actually consists of four continental islands (hence the alternative name of the Yap Islands).
Yap is notable for its stone money, known as Fé (see photograph at left): large donut-shaped, carved disks of (usually) calcite, up to 4 m (12 ft) in diameter (most are much smaller). The islanders know who owns which piece, but do not necessarily move them when ownership changes; their size and weight (the largest ones require twenty adult men to carry) make them very difficult to steal. There are five major types: Mmbul, Gaw, Ray, Yar, and Reng, this last being only 0.3 m (1 ft) in diameter. Their value is based on both size and history, many of them having been brought from other islands, as far as New Guinea, but most coming in ancient times from Palau. Approximately 6,800 of them are scattered around the island. As no more disks are being produced, this ceremonial money supply is fixed (Washington Post, 1984). The United States dollar is the currency used for exchange in Yap.
Yap Proper (known as Wa'ab or Waqab) was initially settled by ancient migrants from the Malay Peninsula, the Indonesian Archipelago, New Guinea and the Solomon Islands. The Yapese language is related to the Malay languages of Southeast Asia, though with strong New Guinean influences. In contrast, the people of Yap's outer islands are descendants of Polynesian settlers, and as such have significant ethnic dissimilarities from the people of Yap Proper. Their culture and languages (Ulithian and Woleaian) are closely related to those of the neighboring islands of Chuuk.taken from wikipedia, here.