Rendering is kind of like cooking, but it's not a kind of cooking that you do in your kitchen. It's actually a way to take animal parts that can't be eaten by people, like bones, fat, and organs, and turn them into other things.
First, the animal parts are collected and brought to a rendering plant. Then they are put into a big machine called a cooker. The cooker heats up the animal parts and melts the fat.
After the fat is melted, it is separated from the other parts of the animal. The fat is used to make things like soap, candles, and other products. The other parts of the animal are turned into something called "meal," which can be used to make animal feed.
So, basically, rendering is a way to take parts of animals that can't be eaten and turn them into other useful things. It's a bit like recycling, but for animals.