Have you taken aglebra in school? Remember when you learned about functions? Such as
f(x) = x + 5, so that
f(1) = 6,
f(2) = 7, etc.?
Well, the definition of the function, f(x) = x + 5, is kind of like the definition of a
Java method:
So in your case, when we call the method go(), it takes its argument, multiplies it by 2, and returns the result. It's like we defined a function
go(x) = x * 2 and then we "call the function" (invoke the method) on line 6 of your code: