When you have a problem with your computer program, sometimes it can be hard to figure out what is going wrong. Shotgun debugging is when you try lots of different things to try and fix the problem, even if you don't really know what you're doing. It's kind of like shooting a shotgun at a target – you don't know exactly where the problem is, so you try lots of different things and hope something works.
But just like shooting a shotgun at a target, shotgun debugging can be really messy and not very effective. It's much better to try and figure out specifically what the problem is, and then use a careful and targeted approach to fix it. That way you can be much more confident that you're actually solving the problem, and not just making things worse!