libexo is an extension library for Xfce. While Xfce ships with quite a few libraries that are primarly targeted at desktop development, libexo is targeted at application development, with a focus on applications for Xfce. It contains several additional widgets (e.g. an icon bar and widgets that automatically ellipsize text), provides a framework for editable toolbars, light-weight session management support, functions to automatically synchronize object properties, and several miscelleanous utility and helper functions useful for application developers.
Terminal is a modern terminal emulator for the Unix/Linux desktop, primarly for the Xfce desktop environment. It was developed because Xfce needed a lightweight and easy-to-use terminal emulator that didn't require the user to install the GNOME libraries, but still provided a worthy alternative to the GNOME terminal emulator, with all the bells and whistles.