Growth theory is like a story about how things get bigger and better over time. Imagine you have a plant. When you first planted the seed, it was tiny and didn't have any leaves or flowers. But as you watered it and gave it sunlight, it started to grow. It grew leaves and then flowers, and eventually became a big, beautiful plant.
In the same way, growth theory is about how things in the world grow and become better over time. For example, a country's economy can also grow. In the past, people used to do things by hand, like farming or making clothes. But over time, people invented machines that could do things faster and better. This made it easier for people to make more things, like food or clothes. And when people can make more things, they can sell them for money and become richer.
Another example is technology. Think about how phones used to be big and clunky, and could only make calls. But now, phones are much smaller and can do so much more - like take pictures, connect to the internet, and play games. This is because people keep coming up with new ideas to improve things, and that's what growth theory is all about - trying to figure out how we can keep making things better and better over time.