Rat tribe is a term used to describe people who live in underground spaces or basements in big cities like Beijing, China. These spaces are often rundown and unregulated, meaning that they are not approved by the government as safe places to live.
Imagine that you're playing hide and seek with your friends in a big city. You might hide in a park or behind a building, right? But some people in the big cities like Beijing, they hide in these underground spaces or basements, similar to what you might use to play hide and seek. These people are called the rat tribe because rats are known to live in dark and secluded places, just like these underground spaces.
Sometimes, people who live in these spaces do so because they don't have enough money to pay for an apartment or house above ground. Other times, they might be migrant workers who moved to the city to find work and can't afford to live in a proper apartment.
Although living in these underground spaces can be dangerous and unhealthy, people still choose to live there because it's the only option they have. It's important that cities and governments find better ways to help people who don't have a place to live, so they don't have to resort to living in unsafe and unregulated spaces.