What is a variable capacitor used for in the oscillatory circuit of the input circuit of a radio receiver?

Due to the fact that radio waves come from many radio stations operating at different frequencies, the receiving antenna is connected to an oscillating circuit containing a variable capacitor. By changing the capacitance of the capacitor, you can achieve the coincidence of the frequency of free oscillations in the circuit with the frequency of the electromagnetic wave of a particular radio station. Due to resonance, the amplitude of the forced voltage fluctuations of the required frequency increases sharply.