Slow Sync Flash Photography

1.  Two ways to get photographs in low light is to use flash or using slow shutter speed.
2.  Disadvantages to using both of those methods is that if you use the flash on your camera, he subject can be too bright and if you use a slow shutter speed you could get some blur due to movement.
3.  A solution to this problem is to use slow sync flash.
4.  front curtain sync - tells your camera to first the flash at the end of the exposure (flash will fire right before shutter closes)
rear curtain sync - tells your camera to fire the flash immediately when shutter opens