Code for adding rows based on number

Hello. Could someone explain in detail what each piece of this code means/does? Thanks.

Sub Onadd()
   Dim rng As Range
   Dim intRow As Integer
   With Range("Number")
      Set rng = .Cells(Rows.Count, 1).End(xlUp)
      intRow = 1
      Do Until intRow > rng.Row
         If IsNumeric(.Cells(intRow)) And .Cells(intRow).Value > 0 Then
            intRow = intRow + 1
            Rows(intRow & ":" & intRow + .Cells(intRow - 1).Value - 1).Insert
            .Cells(intRow) = 0
            intRow = intRow + .Cells(intRow - 1).Value - 1
         End If
         intRow = intRow + 1
      Loop
   End With
End Sub