xfce4-panel | The Xfce4 desktop environment panel | Mehr ...
This is the panel provided by the Xfce4 desktop project. If you want a multi-functional panel that can even handle plugins and the like, xfce4-panel might be worth a try.
xfce4-panel-dbg | debugging informations for xfce4-panel | Mehr ...
This package contains debugging symbols for xfce4-panel, the panel provided by the Xfce4 desktop project.
xfce4-panel-dev | The Xfce4 panel development files | Mehr ...
In this package, you can find the development files distributed with the Xfce4 panel, the main panel of Xfce4 desktop environment. The files in this package are mainly going to be of interest for you if you intend to code applications which use some of the Xfce4 C panel functions.