What changes did the Khmer Rouge bring to Cambodia?

The Khmer Rouge destroyed the whole Cambodian systems of government, business, agriculture, education, security, civilian lives, culture, religion, environment, trading, and a lot more. Million of people were killed during the Khmer Rouge. Thousand of thousand of Cambodian had forced themselves to leave their homeland and migrated to countries such as: US, France, Australia, Canada, Thailand, Laos, Vietnam.