Final answer:
Side fills are larger speakers compared to wedges, positioned on the sides of a stage to ensure full sound coverage for performers, complementing main monitor systems.
Step-by-step explanation:
Side fills are usually larger speakers than wedges and are placed on the side of the stage facing in. They are used to supplement the main monitor systems, which often include wedges or in-ear monitors, and provide a fuller sound coverage on stage. Unlike wedges that are typically aimed at individual performers, side fills serve to fill in the sonic gaps for areas of the stage that may not be adequately covered by other monitors, allowing performers to move around the stage and still hear the mix well.