Human experimentation in North Korea is when the government tests on people to understand the effects of things like chemicals or diseases. Imagine if a doctor wanted to know if medicine could cure a sickness, and they gave you the medicine to see if it worked, but they did not tell you what they were doing or ask for your permission. This is what happens in North Korea. But instead of testing medicine, they test chemicals and diseases that can be dangerous to people.
This testing can be very harmful to people's health, and some people may even die because of it. The North Korean government does this to gain more knowledge about dangerous things that they can use as a weapon or to keep their people in control. This is very bad and not allowed in most other countries because it is cruel and violates human rights.
It is important to remember that people should always be treated with respect and not be used as test subjects without their permission.