Sidechain compression ducks one sound whenever another plays. The classic use is ducking the bass every time the kick hits, so the two never fight for the low end. Duck pads or reverb to the kick and you get the breathing “pump” that defines a lot of EDM.
You can do it with a stock compressor keyed off the kick, with volume-shaper tools for a precise curve, or with dynamic EQ when you only want to duck a specific frequency band rather than the whole sound.