Qualitative research in criminology is like when you ask someone questions to understand why they do things that are against the law. Imagine you see someone doing something wrong, and you ask them why they did it. They might tell you that they did it because they were hungry and they needed to eat, or because they were trying to protect themselves from someone who was hurting them.
Qualitative research is like that, except instead of just asking one person questions, researchers will talk to a bunch of people who have done something wrong, like steal or hurt someone. They will ask them questions about why they did it, how it made them feel, and what they think should happen to them as a result.
The researchers will then take all of the answers they get from everyone and put them together to try to figure out why people do bad things. This can help lawmakers and law enforcement come up with better ways to prevent crime and punish people who break the law.
So, qualitative research in criminology is basically like asking a lot of questions to understand why people do bad things, so society can figure out how to make things better and safer for everyone.