Codes Explaination

' routine name is Macro1
Sub Macro1()

   
   'declaring variables r and i of type long and mcol of type string.
   'JUst a good practice also stop you from assigning string to variables r or i
   Dim r As Long, mcol As String, i As Long
   
   ' find last used cell in Column A. rows.count gives your number of rows on sheet
   ' basically it is like you go to last row of the sheet and press ctrl and up arrow at the
   ' same time. it will find the last used cell or row 1 if all is blank. that row number
   'is stored in variable r
   r = Cells(Rows.Count, "A").End(xlUp).Row
   
   ' get value of last used cell in column A or column 1 (same thing)
   mcol = Cells(r, 1).Text
   
   
   ' insert rows by looping from bottom
   ' this loop from what ever the value of "r" is , till 2. "i" stores the current loop value and initially starts with r and with each loop is subtracted -1 (step -1 part)
   For i = r To 2 Step -1
   
      ' checking if the cell at row "i" and column "A" is not equal to value mcol
      If Cells(i, 1).Value <> mcol Then
         
         ' the value is not equal to mcol
         
         ' assigning mcol as value of cell at row i and column A
         mcol = Cells(i, 1).Value
         
         ' insert a row after row i
         Rows(i + 1).Insert
      
      ' end of if condition
      End If
      
   
   Next i 'repeat loop
   'end of loop code
End Sub