Why A resonant (tuned) circuit needs two energy storage elements that react oppositely: an inductor stores energy in a magnetic field and a capacitor stores it in an electric field. At one frequency their opposing reactances are equal and cancel, giving resonance at f = 1/(2π√LC). That LC pair is the heart of filters, tuners, traps and oscillator tank circuits.
Watch out A resistor is the tempting pick because it is the other basic passive part, but resistance only dissipates energy and damps the circuit, it does not store energy or create resonance; it just broadens the response and lowers Q.
Resonance takes L and C: the two parts that store energy. Remember f = 1/(2π√LC).