Dependent origination is the idea that everything is connected and has a cause and effect relationship. It is like a big puzzle with many different pieces that fit together to make the whole picture.
Imagine you are building with blocks. If you stack one block on top of another, it will stay up because the blocks are depending on each other. Without the first block, the second block would not be able to stand on its own. Everything in the world is like this - it depends on other things to exist or happen.
This principle applies to everything, even our thoughts and emotions. If we have a certain thought or feeling, it is because of something that happened before it. For example, if you feel happy because you got a new toy, the happiness depends on the toy. Without the toy, you would not be happy.
Dependent origination is important to understand because it shows us how everything in the world is connected and affects each other. It also teaches us that everything is impermanent and constantly changing. So, we should not cling to things or get too attached to them, because they will always change.