If you want to understand what the code is doing, there's a tool called the DEBUGGER that does that. It's there to debug YOU, not the code. It's there to help you understand what the code is doing. Get to know how to use it, and fast. It'll make your life so much easier from this point on.
I think it's pretty obvious what that code does. It's a very simple operation, but you would already know what that if it was you who wrote the code.
You copied the code from TutorialsPoint.com,
here[
^] and they already explained what that code does.