PNG has steep mountains, deep rivers and thick rainforest. For thousands of years, communities lived in valleys that were very hard to walk between. Each village invented its own way of talking. So instead of one big language, hundreds of small ones grew up side by side - sometimes just over a hill from each other.
Most people in PNG grow up speaking at least three languages: their own village language (called a 'tok ples', meaning 'talk of the place'), a shared everyday language called Tok Pisin, and English at school. Children swap between them as easily as you might swap between maths and music.
Tok Pisin is the language that ties the country together. It uses lots of short, fun-sounding words. 'Gut moning' means 'good morning'. 'Susa' means 'sister'. A helicopter is a 'mixmaster bilong Jesus' - a 'mixer belonging to Jesus'. Many of its words come from English, mixed up with bits of German and local languages.
Linguists - scientists who study languages - come from all over the world to PNG to listen and learn. Some PNG languages are spoken by only a few hundred people, so each one is precious. Children in PNG schools often help write their own language down for the first time.