High speed sync (HSS) greatly expands the shooting freedom especially in bright daylight by allowing photographers to use wide aperture and fast shutter speed. I have covered this topic in a very popular post titled Understanding the Flash Sync Speed. If you want to see a clear explanation of the concept of high speed sync (HSS), here is a video produced by the folks who are behind the very popular Pocket Wizard MiniTT1 and FlexTT5 wireless flash trigger system.
The Pocket Wizard MiniTT1 transmitter and FlexTT5 transceiver mentioned in the video are wonderful in concept but are also very expensive: $199 for the MiniTT1 and $219 for the FlexTT5. For other remote flash triggering and power control systems, please see the recent post titled Remote Flash Wireless Triggering and Power Control.
Keywords: Flash photography, High Speed Sync, HSS, Sync Speed