Allows you to set the volume for various sounds that your device can make.
The volume control is split into different settings for different types of sounds. The categorizations vary between devices, but commonly consist of the following.
Ringtone refers to the volume of the ringing when you receive a call.
Notifications refers to the volume of the message tone when you receive a text message or other notification for which you have enabled sounds, such as an incoming email. Note that if you want to control which types of notifications generate sounds, you need to do this within the respective app. For example, email notification sounds should be enabled or disabled in the email app.
Some devices may combine the Ringtone and Notifications volume setting into a single setting for convenience, or allow you to choose whether they should be combined with a checkbox.
Music & videos refers to the volume of most other sounds that might play as a result of interacting with your device. In addition to the soundtrack of videos and music, this also includes sounds made by websites or by games.
Alarms lets you control the volume of alarms you have set in the clock app. If you device does not have this option, you should be able to control alarm volumes in the alarms section of the clock app.
System lets you control the volume of various little system sounds such as the pressing of keys on the keyboard. On some devices this option may control the noise made by the camera shutter. Some devices may not have this option, and "system" sounds may just fall under another volume setting such as the Music & videos volume setting.