Webcam won`t broadcast

Tonight my webcam seemed to be working when someone I was chatting with could not see anything. In my webcam window,
my photo did not move when I did. When I closed the webcam window and tried to restart it, my computer stopped responding and did nothing. So I restarted the computer. I clicked the cam icon at the top, clicked to allow my camera to broadcast, the camera
window appeared and nothing else happened. I tried closing the window and clicking the icon again. No success. I had it working
earlier but don't remember what I did right or wrong. Also, what is the padlock icon?   Thanks for the help.