Dominic Ongwen is a man from Uganda who was once a soldier in a group called the Lord's Resistance Army (LRA). The LRA is a bad group of people who hurt others and do bad things.
A long time ago, when Ongwen was a little boy, the LRA came to his village and took him away from his family. They made him become a soldier for their group, even though he was just a kid. Ongwen was very scared and sad and he had to do things that he didn't want to do.
As he got older, Ongwen became a leader in the LRA and he did some very bad things, like hurting other people and forcing them to become part of the group too.
Eventually, Ongwen was found by people who wanted to stop the LRA's bad actions. They put him in jail and he was in trouble for all the bad things that he did.
Now, Ongwen is going to court to answer for his actions. He has to tell people what he did and why he did it. This will help everyone understand what happened and make sure that other people don't do bad things like the LRA did in the future.