Difference in writing code in worksheets vs modules?

[expeo]

What is the difference between writing your VBA code within the worksheet itself vs having it saved in a module (or class module)?

 

[JLGWhiz]

What is the difference between writing your VBA code within the worksheet itself vs having it saved in a module (or class module)?

Code written in the numbered modules (sometimes called public modules) can be called from any of the other code modules by simplty using the procedure name. Whereas, code in the worksheets, UserForms and ThisWorkbook code modules require a more complex coding to access or activate them. Worksheet and ThisWorkbook code modules were intended primarily for event code, the code that activates based on something happening like a Click, a change of data values or selecting a different cell to name a few.

Check this link for more details: http://www.cpearson.com/excel/codemods.htm