Roelof correct Filtering. But only in AC power. RC uses DC power. Capacitors in DC is a storage for voltage like 4-6v, which mostly all ESC and servos run on. What it does Voltage fluctuates, The caps keep voltage in storage to keep it constant. That why electrolytic capacitor(polarized) are use in RC's. That why most Failsafes and Flight ESC you see capacitors in them. Electrolytic caps when charge it keep voltage in them in definitely, until they are discharge. Most ESC manufacture uses Caps on their products and voids their warranties if not used. Failsafe install b4 the RX on Nitro. Capacitor function hasn't since it invented, filtering in AC, Storage in DC.