Hi Melan,

 This technique is great when you want to say get headlights from traffic to project forward That's what you get with First Curtain Sync. It fires the flash at the top of the exposure, and when that exposure is a significant portion of a second, the streaks from moving subjects continue forward of the flash. Rollover to see the effect of Second Curtain Sync, which fires the flash at the instant the shutter ends the exposure. The "curtain" phrase well that's an obsolete carry-over from film SLRs that had twin curtain shutters.the rollerover effect would give a trailing light

Danny O'Byrne  http://www.digitalartzone.co.uk/

"All the technique in the world doesn't compensate for the inability to notice" Eliott Erwitt