First of all, what exactly is a supply chain? And what's involved in "managing" it?
In simple terms, a supply chain is the process of manufacturing, storing, and shipping a product from point A to point B. For example, it's the journey your cell phone goes through, from creation to warehouse to store shelf to your pocket.
And when you think about where all the different components of your cell phone come from, and how far the final product travels to reach your local store, that's a very complex journey. That's where the management part comes into play.