Pagpag is a Filipino term that literally means "to shake off". It refers to a practice in which people scavenge for leftover food from fast-food restaurants, which they then clean, recook, and sell to people who are looking for cheap food options.
So imagine going to a fast-food restaurant, finishing your meal, and leaving some food on your plate. Instead of throwing it away, the restaurant staff may keep it aside for people who are looking for leftover food. These people come and collect it, take it home, and "shake off" any dirt or other contaminants that may have accumulated on it. They then recook the food, add some extra seasoning, and sell it to people who are looking for a cheap meal option.
While pagpag is seen as a way for some people to make ends meet and provide food for their families, it has also been criticized for posing health risks. The leftover food, which may have sat out for hours, or even days, can lead to food poisoning and other health issues if not properly cleaned and cooked.
In summary, pagpag is a practice in which people scavenge for leftover food from fast-food restaurants, clean and recook it, and sell it to people looking for cheap meal options.