Dump digging is when people dig through old garbage dumps to find things that got thrown away. Just imagine dumping everything you don't want in your backyard. That's what people used to do a long time ago. They would take all their trash and dump it in a big hole in the ground. Sometimes, people would throw away things that are still useful like old toys, clothes, tools, or even things like old coins and jewelry.
Nowadays, people who are interested in history or who love finding old treasures will go to these old garbage dumps and look through them very carefully, like searching for hidden treasure. They use special tools like shovels, sifters, and metal detectors to dig up and find the hidden treasures.
However, dump digging can be dangerous because there might be harmful chemicals, sharp objects, or glass in the garbage that could hurt the diggers. So it's important to be very careful when you do it. But it's also a great way to learn about the past and find things that people have forgotten about!