Unzip a directory from a macro VBA Excel

Hi everyone,

(Sorry for the English but I'm French ^^' )

I start on VBA macro, I would like to understand a script that I have found on the Web to unzip a directory and allow me to take the executable .exe.

Option Explicit 
 
Sub Unzip() 
Dim FSO As Object 
Dim oApp As Object 
Dim DossierZip As Variant 
Dim DossierDezip As Variant
Dim UserAct As String

    UserAct = Environ("Username")
     
    DossierZip = "C:\Users\" & UserAct & "\Downloads\test.zip"
    DossierDezip = "C:\XXX\Test"
 
    Set FSO = CreateObject("Scripting.FileSystemObject" ) 
    If FSO.FolderExists(DossierDezip) Then 
        FSO.DeleteFile DossierDezip & "\*.*", True 
        FSO.DeleteFolder DossierDezip & "\*.*", True 
    End If 
    Set FSO = Nothing 
 
    If CreationDossier(DossierDezip) Then 
 
        Set oApp = CreateObject("Shell.Application" ) 
        oApp.Namespace(DossierDezip).CopyHere oApp.Namespace(DossierZip).items 
        Set oApp = Nothing 
 
        Application.StatusBar = "Les fichiers Dézippés se trouvent dans : " & DossierDezip 
    End If 
End Sub

And

Private Function CreationDossier(ByVal sChemin As String) As Boolean 
Dim i As Integer, sTmp As String, Ar() As String 
    If InStr(sChemin, ":" ) = 0 Then 
        Ar = Split(CurDir & "\" & sChemin, "\" ) 
    Else 
        Ar = Split(sChemin, "\" ) 
    End If 
 
    sTmp = Ar(0) 
    ChDrive sTmp 
 
    For i = LBound(Ar) + 1 To UBound(Ar) 
        If Ar(i) <> "" Then 
            sTmp = sTmp & "\" & Ar(i) 
            On Error Resume Next 
            MkDir sTmp 
            On Error GoTo 0 
        End If 
    Next i 
 
    If Dir(sChemin, vbDirectory) = vbNullString Then 
        CreationDossier = False 
    Else 
        CreationDossier = True 
    End If 
End Function

If someone could comments the script to light me ^^

Thanx for your help