About parameters in function

Question

func rangeLength(start : Int, end : Int) -> Int{
return end - start
}
In this code above I used parameters end and start inside function. What will happen if I use another variables corresponding to start and end variables. Do I see any changes? For example

func rangeLength(start : Int, end : Int) -> Int{
var startingPoint = 0
var endingPoint = 0
return startingPoint - endingPoint
}

Can anybody explain me ?

Answer 1

You get what the variables have:
startingPoint = 0
endingPoint = 0
So:
startingPoint - endingPoint = 0 - 0
So:
'return startingPoint - endingPoint' returns 0.

Since no code uses the variables created by function parameters, nothing happens to these variables.