When a person is accused of doing something bad, like breaking the law, sometimes people want to make sure that this person is able to understand what they did was wrong and how the justice system works. This is called a competency evaluation. It is like when your teacher gives you a test to see if you understand a subject before moving on to the next one.
Doctors and specialists who know a lot about these things talk to the accused person and ask them questions to see if they understand what is going on. They might ask questions like, "do you know why you are here today?" or "do you know the difference between right and wrong?"
If the person passes the evaluation, it means they are able to understand what they did and can go on with their trial. But if they don't pass the evaluation, it means they might need extra help to understand what they did was wrong, and they might need to go through more evaluations and treatments before they can stand trial or be punished.