Forklaring af kode

Jeg fik følgende kode af olebole, men forstår ikke helt tankegangen, jeg vil meget gerne have den forklaret (helst af olebole :)) På forhånd tak :)

Private Sub ColorPicker(R As Integer, G As Integer, B As Integer)
    Dim X As Integer
    Dim Y As Integer
    Dim xR As Single
    Dim xG As Single
    Dim xB As Single
    Dim yR As Single
    Dim yG As Single
    Dim yB As Single
    Dim pR As Integer
    Dim pG As Integer
    Dim pB As Integer
 
    For Y = 0 To 255
        For X = 255 To 0 Step -1
            yR = R - (R / 255) * Y
            yG = G - (G / 255) * Y
            yB = B - (B / 255) * Y
         
            xR = (255 - (yR + Y)) / 255
            xG = (255 - (yG + Y)) / 255
            xB = (255 - (yB + Y)) / 255
 
            pR = yR + (xR * (255 - X))
            pG = yG + (xG * (255 - X))
            pB = yB + (xB * (255 - X))
         
            Picture1.PSet (X, Y), RGB(pR, pG, pB)
        Next X
    Next Y
 
    For Y = 0 To 255
        hsb2rgb 360 - ((360 / 255) * Y), 100, 100
        For X = 0 To 20
            Picture2.PSet (X, Y), RGB(rgbA(0), rgbA(1), rgbA(2))
        Next X
    Next Y
 
    Picture1.Visible = True
    Picture2.Visible = True
End Sub

Spørgsmålet hvor jeg fik koden er her: http://www.eksperten.dk/spm/589381