Pacific Islanders are Austronesian people who originated from the Malay Archipelago. Unlike their brethren in Indonesia, Malaysia, Philippines, etcetera; The Austronesian people who had discovered and settled Polonesia (and the rest of oceania), lost all ties with Mainland Asia and never experienced the varied waves of migration that occured between the mainland and the Malay Archepelago, a fact that seperates those who are ethnically Asian and Pacific Islander. Filipinos, Indonesians, and other Malays of that region are much more "Mixed" with other Asian ethnicities and have their own culture which distinguishes themselves from the Pacific Islander ethnicity which has its roots in Polonesia (and also micronesia & melanisia).
Pacific Islanders consist of:
Polynesians, Tongans, Samoans, Niueans, Cook Islanders, Tahitians, Hawaiians, Marquesans, Mâori, Marshall Islanders, Palauans, Mariana Islanders, Nauru, Kiribatians, Guamanians, Wake Islanders, Fijian, New Caledonian,
New Guinean, Maluku Islander, Solomon Islander, Torres Strait Islander, Vanatuan and many more I can't think of.