Resonant circuits, also known as tuned circuits, are electrical circuits designed to resonate at a specific frequency. They typically consist of an inductor and a capacitor, which work together to store and release energy. When the circuit is energized, it can oscillate at its natural frequency, allowing it to selectively amplify signals at that frequency while filtering out others. These circuits are widely used in various applications, including radio transmitters, receivers, and filters. By adjusting the values of the inductor and capacitor, engineers can tune the circuit to the desired frequency, making resonant circuits essential for effective communication and signal processing.