Cores are special things that are made to help create different types of products. They're kind of like the skeleton of the product because they help hold everything together.
Think about making a sandcastle at the beach. You can't just pile up sand because it will fall apart. But if you use a bucket to make a shape and then you fill that shape with sand, you can make something that looks like a real castle. The bucket is like a core – it helps you make a shape that you can work with.
When people make things like pipes or engine parts, they use cores to make sure everything is just the right shape. They'll start by creating a model of the final product, which is kind of like making a sandcastle in a bucket. Then they'll use that model to make the core, which is usually made out of something like sand or clay.
Once they have the core, they can pour liquid metal or plastic around it. As the metal or plastic hardens, it will take on the shape of the core. Then the core is removed, leaving the finished product behind.
So basically, cores are used in manufacturing to make complicated shapes easier to create. They help hold everything together while the product is being made, and then they're removed once the product is finished.