When grown-ups talk about the Indonesian mass killings of 1965-66, they're talking about a really sad time in Indonesia's history. It started when some powerful people disagreed with the government and decided to do something about it. They got together and made a plan to try to take over the government.
But when their plan failed, they started blaming other people for what happened. They said that those people were secretly working with the Communists, who were the enemies of Indonesia. Even if some of those people weren't actually Communists, they were still accused of being a part of this big conspiracy.
It was a really scary time for a lot of people in Indonesia. The people who were accused of being a part of this conspiracy were taken away by the military and never seen again. Some people think that hundreds of thousands of people might have been killed during this time.
This is a really sad story about what can happen when people use violence and fear to try to take control. That's why it's important for us to always treat each other with kindness and understanding, no matter what our differences might be.