Recycling things helps the earth because it reuses the materials to make new products and so you don't have to use more of the earths natural resources to make new products.
For example when you recycle an aluminum can it then can be melted down and made into more aluminum cans or even into something else aluminum.
That means that you don't have to mine for new aluminum ore to make more aluminum cans or other aluminum products.
Or when you recycle a broken down scrap car or other vehicle the vehicle is then crushed and then ground up in a car shredder and then the metal is melted down to be made into other cars and other products that require the metal.
When you recycle the metals or other materials they can then be used over and over again.
You save the earths natural resources because you don't have to mine for those ores or use oil to make plastics etc to get the new products made.
Earth has a lot of iron ore, aluminum ore etc but we still need to recycle what we have.