Okay kiddo, so you know how when we throw our garbage away, it goes to a big pile of trash called a landfill? Well, inside that pile of trash, something called gas is made. This gas is called landfill gas.
Now, instead of just letting the gas sit in the landfill and pollute the air, some grown-ups came up with a way to use it to make things work. They collect the gas and clean it up so it's safe to use. Then they can use it like regular gas to power things like generators or even cars.
So basically, instead of just throwing away our garbage and letting gas pollute the air, we can use the gas to make things work!