Indonesian (Bahasa Indonesia), is the official language of the Southeast Asian nation of Indonesia. With 23 million native speakers, it is spoken by less than 10% of the country`s population as a native language, but is the lingua franca for Indonesia`s diverse linguistic and ethnic groups. It is the language of government, media, education, business, and interaction with Indonesians from different regions.
The vast majority of Indonesia`s population speak another Indonesian language (of which there are hundreds) as their first language (Javanese being the most prominent) but are also fluent in Indonesian. But as more and more Indonesians move to major cities or to different regions, more children are growing up with parents from different regions who speak Indonesian at home.
Indonesian is a standard form of Malay, and is very similar to the Malay language of Malaysia. They are arguably the same language, though there are differences in accent and vocabulary. The grammar is the same, and the large majority of vocabulary is the same.
Malay was chosen to be the national language of Indonesia in 1945 after gaining independence, because it was not the native language of any major ethnic group (to avoid the perception of cultural domination), and because Malay had already been the lingua franca of the entire archipelago for centuries and would be easy for the population to adopt.
Its relative simplicity may have also been a factor in choosing it for mass adoption. Indonesian grammar is straightforward and its verbal system is known as one of the simplest.