Okay, so Article 15 is a part of the Constitution of the Democratic Republic of the Congo which is like a big rule book that says how the country should be run. This particular article talks about how people who are accused of doing something wrong should be treated fairly.
Let's say you have a little brother, and he takes a cookie from the cookie jar without asking. You tell your mom what happened, and she wants to punish your brother. But before she does anything, she should listen to what your brother has to say to make sure he really did take the cookie. That's what Article 15 is all about, making sure that people accused of doing something wrong get a fair chance to explain what happened and to defend themselves.
It's important to treat people fairly because sometimes people can be wrongly accused, and if they don't get a chance to defend themselves, they might get punished for something they didn't do. If someone does something wrong, it's important to make sure they get a fair punishment that fits the crime. That's why Article 15 is so important, it helps make sure that everyone is treated fairly and the right thing happens.