If you have any third party add-ins installed then these will be displayed on an additional Add-Ins tab.
This tab will contain any commands that were previously added to menus or toolbars.
Two groups will be displayed one called "Menu Commands" and one called "Custom Toolbars".
Depending on what other add-ins you have loaded you may or may not see the Add-ins tab displayed. The add-ins tab is only displayed when a 2003 add-in with menu or toolbar customisations is loaded.
For example if the only add-in you have installed is the Analysis-ToolPak then the add-ins tab will not be displayed.
This tab is the default location for any custom UI created in versions of Excel prior to Excel 2007
This tab is also the recommended place for add-ins to put their commands
Built-in Menu Commands
Anything added to the built-in menus.
Built-in Toolbar Commands
Anything added to the built-in toolbars.
Any custom toolbars.