VB programming tutor 1 hour

I have a fairly simple program in VB. I would like someone to spend an hour explaining how it works. I used to write some VBA macros but I am not familiar with some of the stuff in this program. The input for the program is a csv file and the output will also be a csv file. I will paste it in below. Thanks! Public Class Form1 Dim finput As String = "input.csv" Dim groupdata As String = "groupdata.csv" Dim output As String = "output.csv" Dim data(205, 27) As Double Dim va(205), vb(205), v As Double Dim gr(205), g As Byte Private Sub button1_Click(ByVal sender As [login to view URL], ByVal e As [login to view URL]) Handles [login to view URL] inp() run() out() End Sub Public Sub run() Dim a, b As Integer Dim tmp As Double For a = 1 To 205 va(a) = calaver(a, gr(a)) For b = 1 To g If b <> gr(a) Then tmp = calaver(a, b) If tmp < vb(a) Or vb(a) = 0 Then vb(a) = tmp End If End If Next v = v + (vb(a) - va(a)) / max(vb(a), va(a)) Next v = v / 205 End Sub Function max(ByVal v1 As Double, ByVal v2 As Double) As Double If v1 >= v2 Then max = v1 Else max = v2 End If End Function Function calaver(ByVal fr As Integer, ByVal ds As Integer) As Double Dim a, b, n As Integer Dim tmpv, result As Double result = 0 n = 0 For a = 1 To 205 If gr(a) = ds And a <> fr Then tmpv = 0 For b = 1 To 27 tmpv = tmpv + (data(fr, b) - data(a, b)) ^ 2 Next tmpv = tmpv ^ 0.5 n = n + 1 result = result + tmpv End If Next result = result / n calaver = result If n = 0 Then calaver = 0 End Function Public Sub inp() Dim fn, a, b As Integer fn = FreeFile() FileOpen(fn, finput, [login to view URL]) For a = 1 To 205 For b = 1 To 27 Input(fn, data(a, b)) Next Next FileClose(fn) FileOpen(fn, groupdata, [login to view URL]) For a = 1 To 205 Input(fn, gr(a)) If gr(a) > g Then g = gr(a) End If Next FileClose(fn) End Sub Public Sub out() Dim fn, a As Integer fn = FreeFile() FileOpen(fn, output, [login to view URL]) For a = 1 To 205 WriteLine(fn, va(a), vb(a), (vb(a) - va(a)) / max(vb(a), va(a))) Next Write(fn, v) FileClose(fn) End Sub Private Sub Button2_Click(ByVal sender As [login to view URL], ByVal e As [login to view URL]) Handles [login to view URL] End End Sub End Class