If your webcam isn't working and/or you see the this symbol when opening the Camera app:
...
Is the shutter open or closed (red) on the webcam?
If it is closed, then you will need to physically slide it to the right to open in order to use it (there is a tab above the webcam).
Have you restarted the computer and tried again?
Click the 'Start' button, type camera and then press 'Enter' to test it.