The Audio Volume widget on the bottom panel allows you to perform the following tasks.

Task Description
Select the active output device Select any of the available output devices to change the active output device of your system.
Select the active input device Select any of the available input devices to change the active input device of your system.
Control the volume of a device Use the sliders to adjust the master volume of an input/output device.
Adjust the volume for a specific app The Volume tab allows you to control the volume for a specific application.
Open the audio settings Click the Configure Audio Devices button to open the audio configuration screen in System Settings.