Complex sentence: Snowboarding is a winter sport that involves descending a slope that is covered with snow while standing on a snowboard, a board attached to a rider's feet, using a special boot set into a mounted binding.
Split into simpler sentences: Snowboarding is a winter sport that involves descending a slope that is covered with snow while standing on a snowboard attached to a rider's feet. The snow board is attached using a special boot set into a mounted binding.