Widgets are small utilities you can add on your desktop. They allow to display information about weather, currency exchange, email alerts, or system resources (CPU, Graphics Card, etc.).
To be able to use widgets on Ubuntu, you can install Screenlets which is a widget application that has a considerable number of applications.
To install Screenlets on Ubuntu, launch the terminal and issue this command:
sudo apt-get install screenlets
To start Screenlets, open Application > Accessories > Screenlets. To start Screenlets automatically on each Ubuntu startup, check on "Auto start on login" in the main interface of Screenlets.