Ubuntu's default desktop environment is Unity. It's made up of the desktop background, a horizontal menu bar at the top, and a vertical bar on the left called the Launcher.
Manages network connections so you can quickly connect.
An easy way to adjust the sound volume.
Shows the current keyboard layout (En, Fr, Ku, etc.).
Links to system settings, Ubuntu Help, user/guest sessions, restart, or full shutdown.
Shows the current time and links to calendar, time and date settings.
The vertical bar of icons on the left for quick access to applications, mounted devices and the Trash. Icon size is changed via Session Indicator → System Settings → Appearance.
Click an icon on the Launcher to run it; a running app shows one or more triangles beside its icon (one per open window).
Open the Dash, find the app, and drag its icon to the Launcher — or right-click a running app's icon and choose "Lock to Launcher."
Right-click the app's icon on the Launcher and choose "Unlock from Launcher."
Helps you quickly find applications and files — locally (installed apps, recent files) and remotely (Twitter, Google Docs, etc.), similar to the Windows Start menu/Start Screen.
Every window has a title bar with the app's name, plus close/minimize/maximize buttons in the top-left corner.