What is the difference between Sub and Function in VB6?

Question

I am going through some old VB code and I run into function definitions like these -

 Private Function ExistingCustomer(Index As Integer, Customer As String)         


        

Answer 1

They are both sections to write code however a function must return a value. For example if you had a program in which a complicated mathematical procedure needs to be executed a number of times you would simply make a function and have the complicated maths code in there and any time you need to do the calculation you can just call the function. Hope this helped not sure if I explained it well.