AddressOf

Most of the time you will not need to obtain any low level information about your variables.
However there are a few Windows API functions that require the memory address of a variable.

link - learn.microsoft.com/en-us/office/vba/language/reference/user-interface-help/addressof-operator 

Declare Function EnumFontFamilies Lib "gdi32" Alias _ 
     "EnumFontFamiliesA" _ 
     (ByVal hDC As Long, ByVal lpszFamily As String, _ 
     ByVal lpEnumFontFamProc As Long, LParam As Any) As Long 

Declare Function GetDC Lib "user32" (ByVal hWnd As Long) As Long 

Declare Function ReleaseDC Lib "user32" (ByVal hWnd As Long, _ 
     ByVal hDC As Long) As Long 

Sub FillListWithFonts(LB As ListBox) 
   Dim hDC As Long 
   LB.Clear 
   hDC = GetDC(LB.hWnd) 
   EnumFontFamilies hDC, vbNullString, AddressOf EnumFontFamProc, LB 
   ReleaseDC LB.hWnd, hDC 
End Sub 

When you want to use API functions the following functions will prove useful:
VarPtr - returns the address of a variable
VarPtrArray - returns the address of an array
VarPtrStringArray - returns the address of an array string
StrPtr - returns the address of the UNICODE string buffer
ObjPtr - returns the pointer to the interface referenced by an object variable