Have you ever made soup with your mom or dad? You put some vegetables and meat in a pot with water, and then you let it cook on the stove for a while. After a while, you take out the vegetables and meat, and now you have soup!
Decoction is kind of like making soup, but with herbs instead of vegetables and meat.
First, you put the herbs in a pot of cold water. Then you heat it up slowly, stirring it every so often. Once it starts to boil, you turn down the heat and let it simmer for a while.
After a while, you take out the herbs, just like you would take out the vegetables and meat when you make soup. The liquid left behind is what you use as medicine. It has all the good stuff from the herbs, and because you simmered it for so long, it’s really concentrated.
So, decoction is a way to make really strong medicine from herbs, kind of like making soup!