Short answers, pulled from the story.
There are three species of orangutan: the Bornean orangutan (Pongo pygmaeus), the Sumatran orangutan (Pongo abelii), and the Tapanuli orangutan (Pongo tapanuliensis), identified definitively in 2017. All three are found only on the islands of Borneo and Sumatra in Southeast Asia.
All three orangutan species are listed as critically endangered by the IUCN. The primary threats are habitat destruction from palm oil plantation expansion and logging, poaching for bushmeat and the illegal pet trade, and conflict with local communities whose agricultural land orangutans sometimes raid after losing their forest homes.
The word orangutan comes from the Malay words orang, meaning person, and hutan, meaning forest. The phrase originally referred to forest-dwelling people; Dutch physician Jacobus Bontius first applied it in print to the ape in 1631, and it entered English in 1693 in the form Orang-Outang.
Orangutans are among the most intelligent non-human primates. They have been documented to pass the mirror self-recognition test, practise calculated reciprocity, plan travel routes in advance, use and store tools, and teach their young through deliberate alarm-call delay. Zoo Atlanta maintains a touch-screen computer system for its Sumatran orangutans to play games on.
Biruté Galdikas is a primatologist who pioneered field studies of wild orangutans after arriving in Borneo in 1971. She established Camp Leakey in Tanjung Puting and developed her PhD thesis for UCLA there. She is counted alongside Jane Goodall and Dian Fossey as one of Leakey's Angels, and she later founded Orangutan Foundation International.
The Tapanuli orangutan (Pongo tapanuliensis) was identified as a distinct species in 2017 and lives only in the Batang Toru forest of Sumatra south of Lake Toba. It is significant because, despite sharing Sumatra with the Sumatran orangutan, it is genetically more closely related to the Bornean species. Fewer than 800 individuals are estimated to survive, making it one of the most endangered great apes.