Indonesia (or Bahasa Indonesia) is a form of the Malay language, thought to be based on the Riau dialect. Because of divergence with other forms of Malay (mainly due to the Dutch and Javanese influences on Indonesian), Indonesian is now usually considered a distinct language.
Most people in Indonesia also speak another local language, and possibly also other widely-used languages such as English. Bilingualism, and the similarity with Malay, makes speakers of Indonesian hard to count. The majority of speakers are in Indonesia, where nearly everyone speaks it as either a first or second language. There are also a good number of speakers in Timor-Leste, where it was used in education during the period of Indonesian control, in the Philippines, and the Netherlands from the period of the 'Dutch East Indies' colony. Indonesian speakers numbering tens of thousands are also found in the United States and Australia.