VBA Code

The difference between "ThisWorkbook" and "ActiveWorkbook" refers to the workbook that is currently in the active window, whereas "ThisWorkbooK" refers to the workbook where the code is actually running from.

loop through all the worksheets
loop through all the workbooks in a folder

Activating and Selecting

Workbooks("Wbk1.xls").Activate 

Can be used if the workbook is new and has not yet been saved.

Workbooks("Book3").Activate 
Workbooks("Book3.xls").Activate 

assuming that the workbook has been saved

Workbooks.Item(2).Activate 

This refers to the workbook that contains the code.

ThisWorkbook. 

ThisWorkbook

This is always the workbook that contain the code.

Application.ThisWoorkbook 
ThisWorkbook 

ActiveWorkbook

This is the worksheet that is currently active or selected

Application.ActiveWorkbook 
ActiveWorkbook 
ActiveWorkbook.Path = "C:\Temp" 
ActiveWorkbook.Name = "Book2" 

Application.Height 
Application.Left 
Application.Top 
Application.Width 

Application.UsuableWidth 
Application.UsuableHeight 

Application.ProductCode 
Application.Hwnd 
Application.MemoryUsed 
Application.UsedObjects 

objWorkbook.CreateBackup = False 

FullName

There is only a folder path when the workbook has been saved
This property is equivalent to the Path property, followed by the current file system separator, followed by the Name property.

ActiveWorkbook.FullName 

Determines the version of a workbook, i.e. which version of Excel created this workbook.

ActiveWorkbook.FileFormat 

16 = Excel 2
29 = Excel 3
33 = Excel 5
39 = Excel 5/96
-4143 = Excel 97/2000/2002/2003

undo the last action performed by the user interface.

Application.Undo 
Application.Repeat 

Returns the collection of recently opened files

Application.RecentFiles 

Read-only returns an object allowing manipulation of the office assistant.

Application.Assistant 

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AnswerWizard

There's only one Answer Wizard per application, and all changes to the AnswerWizard or the AnswerWizardFiles collection affect the active Office application immediately.

Application.AnswerWizard 
Application.AnswerWizard.ResetFileList