Most Microsoft Excel add-ins can be divided into two broad categories: add-ins that work with Microsoft Excel (committee), and add-ins that take over the complete workspace (dictators). Each type of add-in requires unique considerations by the programmer.
Committee add-ins generally provide additional functionality to Microsoft Excel. They make few, if any, changes to the workspace and are used during the normal course of Microsoft Excel operation. All of the add-ins that ship with Microsoft Excel are committee add-ins (that is, Solver, AutoSave, Web Form Wizard, and so forth). They extend the spreadsheet environment and add specialized functionality.
Dictator add-ins are usually special-purpose, custom add-ins that run within the Microsoft Excel environment. These add-ins tend to make extensive changes to the workspace, often to the point that it is not obvious that Microsoft Excel is hosting them. Custom menus and toolbars are standard features with these types of add-ins.