High-speed sync (HSS)
Flash feature that allows the use of shutter speeds with flash, faster than the usual sync speed. The flash pulses at high frequency to ensure even exposure, even though the shutter blinds are never fully open during the exposure. The facility is useful for freezing close-up action in daylight, and for allowing the widest apertures even in bright light.
Sources: Pixabay, NASA, Wikipedia, Susan Wingfield Lamar High School