The a parameter is part of the definition of the function / sub (collectively referred to as methods). When you need to pass a value (called an argument) to that method, you can pass a literal value or the value of a variable (Value1, in your example).
So, a function like this:
Public Function Add (ByVal a As Integer, ByVal B As Integer) As Integer
Return a + b
can be called like this:
Dim result As Integer = myCalculator.Add(2, 4)
or like this:
Dim value1 As Integer = 2
Dim value2 As Integer = 4
Dim result As Integer = myCalculator.Add(value1, value2)
There's no relation in name between the parameters of the method, and the values you pass to it.
Maybe this helps: http://msdn.microsoft.com/en-us/libr...(v=vs.80).aspx