1. Check this box to enable live view if you are using a webcam or an SLR that supports live view. Options include, when live view shows or if live view pauses and for how long. You can also set how the camera is turned and if you want it mirrored.
2. Most SLR cameras require at least a 1 second pause to auto focus or trigger an external flash.
3. Most Canon cameras require the checkbox "External Flash Compensation" for the live view to be bright with an external flash and Manual exposure. Many higher end cameras have an "exposure simulation" mode that needs to be turned off in the camera menu as well.
4. Clicking the "Test" button will show a preview of the cameras live view here.