To turn on your iSight camera, open an application that uses a webcam, like "Photo Booth". Your iSight should turn on when an application requires it to do so.

iSight is simply the built-in camera on the Mac. In order to use the iSight camera, you will need to open an application that involves the use of the camera. Some programs include iChat and Photo Booth.

The Apple iSight brand is a line of both external and internal webcams developed by the Apple company. Apple iSight cameras include built-in microphones and have dual-element noise suppression.

Yes it does. Also has a built in microphone and speakers.

The MacBook Air has a built in iSight camera. To add another camera you would need to specify what you wanted to achieve that you could not with the iSight.