求救，哪位大神能解释一下每句的意思吗，初学看不懂，谢谢

小耗子aa

Option Explicit
Dim Sht As Worksheet
Private Sub ListBox1_Click()
    ActiveCell = ListBox1.Text
    TextBox1.Visible = False
    ListBox1.Visible = False
    [a1].Select
    End Sub
Private Sub TextBox1_Change()
Dim rrrr As Range, N%
If TextBox1 = "" Then Exit Sub
ActiveCell = TextBox1.Text
With ListBox1
   .Top = ActiveCell.Offset(1).Top
   .Left = ActiveCell.Left
   .Width = ActiveCell.Width + 125
   .Visible = True
   .Clear
   For Each rrrr In Sht.Range("a1", Sht.[a65536].End(3))
      If InStr(UCase(rrrr), UCase(TextBox1.Text)) > 0 Then
         N = N + 1
         .AddItem rrrr.Value
      End If
   Next
   N = IIf(N > 12, 12, N)
   .Height = 3 + N * 11
End With
End Sub
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
TextBox1.Visible = False: ListBox1.Visible = False
If Target.Address <> "$H$3" And Target.Address <> "$H$6" Then Exit Sub
If Target.Count > 1 Then Exit Sub
If Len(Target.Offset(-1)) < 1 Then Exit Sub
If Target.Address = "$H$3" Then Set Sht = Sheet3 Else Set Sht = Sheet1
   With TextBox1
      .Top = Target.Top
      .Left = Target.Left
      .Height = Target.Height
      .Width = Target.Width + 125
      .Visible = True
      .Text = ""
      .Activate
   
   End With
End Sub