When they use the term 'dumpster diving', does this just mean searching through disposals for gadgets or tech or something else?

A friend of mine worked at a private high school where the students were predominantly from wealthy families in Asia. Especially when they all flew home for summer break, the dumpsters were more like outlet malls. Like-new Nikes, ritzy backpacks - stuff that was more hassle to pack up and ship or fly home. They could afford to buy more.